Formula is not Presenting accurate Result

Question

I have been using below mentioned formula to get the Count, IF there is name/vale in Col"I" then Col"B" will popup a count as available in sheet.

But there is variance in my formula where it is not counting accurately.

I have added a sheet where formula result is available in Col"B" as well as result i'm looking for in col"C".

You help will be appreciated.

Sheet Link https://docs.google.com/spreadsheets/d/1Pkner13t93HBjVTEkVFlDpVnVReVwoRSRIcwf1Q7CpY/edit?usp=sharing

=ARRAY_CONSTRAIN(ARRAYFORMULA (if(LEN(I:I),if(row(I:I)=1,"CASE ID",H2&"_"&TEXT(ROW(B:B)-1,"000")),)),500,1)

Answer 1

use:

=ARRAYFORMULA({"Count"; IF(I2:I="",,"OD_"&TEXT(
 COUNTIFS(I2:I, I2:I, ROW(I2:I), "<="&ROW(I2:I)), "000"))})