Well be assured that the top 20 percentile would be announced way before the counselling for any college such as JOSAA, MHT CET etc starts.

Also, if your score is more than 75% then you need not worry about the top 20 percentile.

All the best for your future admissions!

Varsha,

          Ending percentage of top 20 percentile and your percentile both releases at the time of result declaration only irrespective of any board. You can check previous years' trend of top 2o percentile here https://engineering.careers360.com/articles/top-20-percentile-cutoff-of-class-12-boards-for-iit-admission

Regards