Hello aspirant,

The basic eligibility  for admission through JEE advanced is that you should score atleast 75% in 10+2 exams or its equivalent or be in top 20 percentiles of the board results . The 75% marks are calculated using the marks of all the subject you appeared for. So thats what you have to take care about else you don't need to worry just score good marks in JEE advanced and and your desired IIT.

Hope this helps.

If any queries feel free to ask.

All the best!!

Regards.