Dear student,

First of all you must mention the examination name that for which exam you are targeting. Now assuming, that you are asking about JEE mains exam, then in JEE mains exam for securing under 1000 sc category rank, your percentile score must be above 96 percentile and for that you must secure at least above 200 marks in JEE mains.
But if you are talking about advanced, then a score of above 90 will do good.

Also check out the following link to know the marks vs ranks trends for JEE mains 2020 :-
https://engineering.careers360.com/articles/jee-main-marks-vs-rank