Dear Student,

It doesn't matter how much a candidate have got in 12th Board if you have qualified JEE Mains you will eligible to write JEE Advance but he/she will not allowed to take seat if he/she has got below 75 percent in 12th Board Exam. And I don't think he is qualified for JEE Advance 2019 as he had got 85 percentile which is approximately equal to 60-65 and cutoff for JEE Advance for general candidate is 89.75  for EWS candidate it is 78.21 and for OBC candidate it is 74.31.

Thank You 

Best of Luck!