The result for JEE main is yet to be declared and therefore it is very early to predict the marks vs rank for JEE main 2020.
however the percentile score has been released and you can calculate your approximate rank by using the following formula
(100-percentile score) *(869010)/ 100
if the number of candidates appearing for JEE main April get increased to 12 lakh then the formula for calculation of rank would be
The rank calculated here are in general category