Hi Aashay,

First of all, the marks declared by State board for the top 20 percentile is out 500. That means you have to include 5 subjects whose total must be scaled down to 100. The five subjects which you have to include are as follows:1. Physics 2.Chemsitry 3. Maths 4.any language 5. Any subject other than those mentioned above. Conclusively based on this calculation your percentile will be calculated, only then you decide if you qualify for the top 20 percentile criteria or not.

I hope this helps you and for further information, you can refer the following link

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

All the best.