What is top 20 percentile
Dear Rohit,
In order to take admission in IITs/NITs/IIITs and GFTIs you should have 75% marks in your board exam or you should be in top 20 percentile.
To know about the top 20 percentile and how it is calculated you can refer below link
For IITs
https://engineering.careers360.com/articles/top-20-percentile-cutoff-of-class-12-boards-for-iit-admission
For NITs/IIITs and GFTIs
https://engineering.careers360.com/articles/top-20-percentile-of-class-12-boards-for-nits-iiits-and-cftis
Good Luck!!