To be honest,  its difficult to predict the actual rank or JEE advanced qualifying marks. Neverthless, you may calculate your expected rank by this formula.A percentile is the no.of Candidates who scored better than you in the exam. Going by that, to calculate your JEE percentille, we should use the formula 100 - your total percentile score. Now 869010 Candidates appeared for Jan exam. Going by that, your rank formula  is (100 - your total score) X 869010 /100. And your rank would be 634377. Let's say the number of candidates for April exam increased to 12,00,000 then your final rank shall be (100 - your total score) X 12,00,000/100. At this point in time, it is difficult to predict the JEE Advanced qualifying marks but 85 percentile and above should be an ideal score. You may have to appear for JEE Mains April session.