MIPS not transferring values properly between registers (adding 28 for no reason)

Question

I'm writing a program in assembly that simulates multiplication via iterative addition. I have the algorithm done, and for my first test case, I set my multiplicand to 50. Upon transferring this value, stored in $a0 and transferred to $s0, I get 000001001110 (78) instead of 000000110010 (50). For some reason, an extra 28 is added, and I can't seem to figure out where in my code this is happening. I'll paste all the relevant code, I'm at a loss here and would appreciate any help with streamlining or any oversights I've made. I also do use macros that I've defined in another file, simply for easy printing.

My test file:

.globl main
main:
TEST1: 
    li      $a0,    A
    li      $a1,    BBB
    li      $a2,    6         # n: number of bits 
    jal     ex.3.12 

exit:
    li      $v0,    10
    syscall

my file for 3.12 (the first version of MIPS multiplication by addition)

.include "./cs47.macro.asm"
.globl ex.3.12

.text
    li  $a0,    6
    li  $a1,    7
    li  $a2,    4
    jal ex.3.12
    print_reg ($s4)
    exit
      
ex.3.12:     # 
    addi  $sp,  $sp,  -24
    sw    $ra,  ($sp)
    sw    $s0,  4($sp)
    sw    $s1,  8($sp)
    sw    $s2, 12($sp)
    sw    $s3, 16($sp)
    sw    $s4, 20($sp)

    jal     display.title       # xxx
    print_str_literal ("Step Action          Multiplier  Mutiplicand      Product\n")
    move    $s0,  $a0           #  A = multiplicand
    subi $s0, $s0, 28
    move    $s1,  $a1           #  B = multiplier
    move    $s2,  $a2           #  N = # bits for display, assume N <= 16
    li      $s4,  0             #  product

# xxx print out the initial vals
   print_str_literal ("0    Inital Vals     " )
   print_triple ($s1, $s0, $s4) # xxx print multiplier multiplicand product
   print_newline ()

loop:
    beq     $s2,    $0,  done    #  if index $s2==0 quit loop

    # xxx print out step numbers
    sub     $t0,  $a2,     $s2  # xxx t0 (step number) = N - s2 (index) 
    addi    $t0,  $t0,     1    # xxx t0 --
    print_reg ($t0)             # xxx t0 (step number) = N - 1 - s2 (index)

    andi    $s3,    $s1, 1       #  s3  = right most bit of multiplier s1.
    beq     $s3,    0,   ZERO    #  if s3 == 0, then jump to ZERO
    beq     $s3 1,   ONE
    
ONE: # addition happens
    addu    $s4,    $s4, $s0       #  if s3 == 1, s4 += s0 (multiplicand)
    print_str_literal ("    Prod=Prod+Mcand ")
    print_triple($s1,$s0,$s4)
    j ABC   
    
ZERO :  # no addition
    print_str_literal ("    lsb=0, no op    " )
    print_triple($s1, $s0, $s4)
    j ABC 
    
ABC: 
               # xxx
    sll     $s0,    $s0,   1        #  shift A (multiplicand) 1 bit to the left
        print_reg ($t0)
        print_str_literal("    Lshift Mcand    ")
        print_triple($s1, $s0, $s4)
        
    srl     $s1,    $s1,   1        #  shift B (multiplier) 1 bit to the right
        print_reg ($t0)
        print_str_literal("    Rshift Mplier   ")
        print_triple($s1, $s0, $s4)
        print_newline ()
        
    addi    $s2,    $s2    -1
    
    j       loop

done:
    move  $t0,  $s4
    print_str_literal("\nResult of A*B by iterative addition --> ")
    print_reg($t0)
    
    lw    $ra,    ($sp)
    lw    $s0,  4($sp)
    lw    $s1,  8($sp)
    lw    $s2, 12($sp)
    lw    $s3, 16($sp)
    lw    $s4, 20($sp)
    addi  $sp,  $sp,  24
    
    jr      $ra

The expected first line of results:

***********************************************************
  A=50  B=10  N=6
************************************************************
Step Action          Multiplier  Multiplicand      Product
0    Initial Vals    001010      000000110010      000000000000     

The first line of results that I get without subtracting 28:

************************************************************
  A=50  B=10  N=6
************************************************************
Step Action          Multiplier  Mutiplicand      Product
0    Initial Vals     001010      000001001110      000000000000  

Any help or insights would be greatly appreciated, thank you