Hii

Scoring 82.5 percentile in JEE Mains means that you have scored higher or equal marks to 82.5 % of students who appeared for the exam and that only 17.5% of the total students have scored higher marks than you.
You can use the following links to know more about how the percentiles are calculated and what it exactly means.
https://engineering.careers360.com/articles/jee-main-result
https://engineering.careers360.com/articles/jee-main-normalisation-process-how-scores-are-calculated

Thanks!!!