hi upendra,

I hope you are doing well. Regarding 77.3 percentile, according to 2019 percentile vs rank you can expect you rank to be around 2.25 lakh or more. As you know JEE Mains is of 300 marks from this year(2020), previously it was of 360 marks. So its hard to predict your exact marks. Also it depends on how hard/easy your paper was. So only you know how much you scored exactly. But by very rough estimation your marks will be around 40/300.

I hope this answer will help.
All the best for the future!!

As per your percentile your expected rank would be approx 228000 to 229000 and as per previous year cutoff, the colleges you get are:-

Pune institute of computer technology

JIIT Noida

Amity University Noida

Walchand institute of technology,Solapur

It is difficult to predict your marks as per your percentile.

To know more about your chances of getting other colleges check out the college predictor link below:

https://engineering.careers360.com/jee-main-college-predictor