Hey there!

NTA percentile system takes a lot into consideration than just total score. They have an order of preference while deciding the rank

1. Candidate scoring higher percentile in first subject of the question paper either physics or mathematics gets the highest percentile

2. Candidates who has attempted all three sections gets more percentile than candidate who leaves one section untouched or doesn't answer a lot from a particular section

3. The importance of subjects goes in a descending order i.e, first subject on the screen has highest priority

All of these and some other factors decide the rank that may be why your friend got a better rank even though he scored less. Hope this helps.