Admission to the NIT is based on the rank rather than the percentile, Last year NIT Silchar cutoff rank for the Mechanical engineering under home state quota in ST Category (male) was 2804 via JSAA on the other hand 80730 via CSAB. So you should wait for the final rank of yours. Learn More- https://www.careers360.com/university/national-institute-of-technology-silchar/cut-off?college_id=139&exam_sub_exam_id=2&counselling_id=550&category_of_admission_id=2&caste_id=2&gender_id=1

apart from these here is the more about JEE Main Score vs Marks vs percentile - https://engineering.careers360.com/articles/jee-main-marks-vs-percentile