Percentile is calculated by the ratio of the number of values to the total number of values . You cant say/depict your actual score from your percentile. To calculate the actual score you would need to know the number of students who appeared in the examination and the highest score, average cut offs and the highest score. while as marks are calculated based on the right questions you have attempted, out of the total marks you have obtained for the right number of questions marks from wrong questions marked are deducted from the total.

From this year itself,percentile score is to be considered for jee main ranking.Percentile scores are based on the relative performance of all those candidates who appear for the examination. It obtained after transforming the scores into a scale ranging from 100 to 0 for each session of examinees. Percentile Score shows the percentage of candidates who have scored equal to or below a particular percentile in an exam. It is the normalized score and not the raw scores. After normalization, each topper of a session will get the same percentile of 100 which is the desirable one. Also the marks between the lowest and highest scores are also converted to the respective percentiles. For more details and the for the formula, go to

https://www.google.com/amp/s/engineering.careers360.com/articles/jee-main-normalisation-process-how-scores-are-calculated/amp

Actually ,NTA adopted to declares result in the form percentile score as this year exam is conducted in different session.Total 8 session in which 1st phase of jee mains held this year.It is not easy to maintain level of paper same for each and every session.No students get disadvantage of tough paper that's why percentile method is adopted.It only tells about relative performance of candidates in their respective session.

It is calculated as:(Your raw score × number of candidates who score equal to or less than your raw score in your session)/total number of candidates in that session.

You cna ask if you have any other queries.

GOOD LUCK!