A critical query about CAT exam form filing

The Academic section of the form asks about my maximum marks in 12th grade

So I gave all exams of the main 5 subjects in 12th, and had picked one extra sixth subject which I was absent in, but since only 5 subjects are considered in 12th, I passed with around 91%, and the marksheet has the scores of 5 subjects and the 6th subject as AB (absent)

But the CAT form asks me to fill the max marks of ALL the subjects, so what do i do? This will reduce my percentage unnecessarily if I count the sixth subject too

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