Hello Aspirant. The percentile scores indicates the percentage of candidates that have scored equal to or below that particular percentile in that exam. Therefore the topper will get 100 percentile most probably. The marks obtained between the highest and lowest is also converted to appropriate percentile. This is done so that there is no normalisation of the marks and no student is disadvantaged or benefitted from a particular question paper set. The percentile scores for the total raw score for all the 4 sessions (in january exam) will be merged and that is your NTA score. This will be used for compilation of result and preparation of the Overall merit list after the April 2019 exam results.

For further information about how the percentile is calculated and how results will be prepared check the below link.

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

Also check out the official Jee mains website.

https://jeemain.nic.in/webinfo/Public/Home.aspx