Percentile can be calculated by :

Total Percentile (TP) = 100 x (No. of candidates appeared from the session with raw score EQUAL TO or LESS than T1 score/ Total No. of candidates appeared in the session)

For example,

If there are 100 students and if 95 students have got marks below or equal to 99. Then the student who scored 99 will have a percentile: 100*(95/100)= 95 percentile.

The percentile gives you the percentage of people who have scored less or equal to your score out of the total population appeared for the exam.

I hope this answer helps. All the very best for your future endeavors!