Exam Score Analysis

Please people I still have issues with this analysis.
When we tested the formulas they worked perfectly well.
But when I transferred into my real sheet, the calculation is not accurate.
Note: accurate calculation is the addition of the last four (4) columns in the analysis will equal to the total number present.
These are the formulas I used.
Column 1: =COUNTA(B3:B31)
Column 2: =COUNTIF(S4:S64,">0")
Column 3: =COUNTIF(S4:S64,"0")
Column 4: =COUNTIFS(D4:D64,">=50",E4:E64,">=50",T4:T64,">=49.5")
Column 5: =COUNTIFS(D4:D64,"<50",E4:E64,">=50",T4:T64,">=49.5")
Column 6: =COUNTIFS(D4:D64,">=50",E4:E64,"<50",T4:T64,">=49.5")
Column 7: =COUNTIFS(D4:D64,"<50",E4:E64,"<50")
All in the attached sheet.
Thanks

@oeldere can you please help me edit the formular to that which you desire i use so i can understand better? please