Dear Abhyand, 

If you want best NIT (like NIT Tiruchirappalli) ,then you need to score a minimum percentile of 99 though you belong to EWS Category. 

And if you want CS,then you need to score a minimum of 99.5 percentile. 

Since it is the best NIT though you have a reserved category you need to score good marks .

May be there are less candidates that will competiting for the reserved seat, then you will be lucky to get a seat with your good score. 

HOPE IT HELPS.