Hello Prashant, Greetings!

Well, you will have to mention aggregate percentage of five subjects.

For calculating aggregate for different class 2 th boards, the marks scored in five subjects - (1) Physics, (2) Chemistry, (3) Mathematics, (4) A language and (5) Any subject other than the above four, is taken into account.

You can find more information here:

https://engineering.careers360.com/articles/top-20-percentile-cutoff-of-class-12-boards-for-iit-admission/amp

Thank you, hope this helps.