Hello aspirant,

Hope you are doing well

To get in to iits one needs to write jee mains and jee advanced .

Jee mains is a qualifying exam for jee advanced .

Jee mains give percntiles for students where as jeeadvanced give ranks as per the marks secured.

What ever percentile you got in  jee mains is not required for jee advanced to get in to iit.

One meeds to get top ranks in jee advanced for iits.

Hope this helps you

All the best!