Harshit under the SC category tab if you are able to score above 25% of the marks then you can definitely get into one of the IITs and with 30% marks, you can get a much better rank which can help you in getting some of the good branches in the old IITs. Better the percentage of score better will be your rank. Although these are the parameters based on the last year records and which can change drastically this year. Although on good terms cut-off is expected to fall down so with the same percentage I mentioned above you can get a much better rank.

Feel free to ask if you have any more queries. All the best!!