Hello Aspirant,

The Calculation of the marks & exact rank would be difficult based on your percentile.

100 - your total percentile score is the percentage  of people ahead of you. 874469 are the number of candidates appeared for Jan exam. So rank formula is (100 - your total score) X 869010 /100. If the number of candidates for April exam increased to 1200000 then your final rank shall be (100 - your total score) X 1200000/100.

Using the formula (100 - your total score) X 869010 /100

Your probable rank is 4,34,505

I would suggest you to appear again for JEE Main 2020 April Session & try to score well.

Good Luck!