As per the previous years analysis you need around 191-196 marks to get 99.5 percentile in JEE mains marks. Refer to the website below to check all the percentile and marks comparison..

https://engineering.careers360.com/articles/jee-main-marks-vs-percentile

Having said this cutoffs keep fluctuating from year to year as they depend on various factors like number of candidates appearing and also the paper level difficulty, etc. So just give your best and try scoring 200+ that's it. Rest everything will depend upon time and the top ranker's marks.

Best wishes. Thank you.