Hell student. This is how you can calculate our rank:

Rank Formula = (100 - your percentile) X 9,21,261  /100

here 9,21,261  are the number of students attended for jee mains in january.

SO your rank is 21,883 approximately in january attempt

Rank Formula = (100 - your percentile) X 6,35,000  /100

here 6,35,000  are the number of students attended for jee mains in september

And your rank is 34,033 approximately in september atempt