Hi harsh aggarwal I can't be very sure. But I will try to make use of previous year stats.

Every year cut off score for Top wbjee colleges  increases or decreases acoordingly with lowest branch is around 250-260, which means a rank around 1 thousand. Since around 4-5 lakh students sit for WBJEE Mains, so you need at least 70 percentile to be eligible for all top colleges of wbjee.

hope it will help you. FOR MORE QUERY COMMENT BELOW AND UPVOTE :)