Hello Aspirant. The exact percent of people ahead of you is (100- your percentile score) i.e in your case its 39%. Therefore no. of students ahead of you is 39% of the tot. no. of students appeared (874469) i.e. 341043 students (approx)

Your rank is checked by the following formula-

(100-tot. percentile)*(874469/100)

So your rank is 341043.

But this is not the final rank. Your rank will depend upon the no. of students appearing for the April exam (which will be more oviously). NTA will also consider best of two attempts by candidates who will be appearing twice.

According to previous years cutoff ranks a rank below 2,00,000 will qualify for JEE Advanced.

For more details check the below link.

https://www.entrance360.com/engineering/how-to-calculate-rank-for-jee-mains-2019/

Hope this helps. You can comment down below for any other questions.