For JoSAA counseling, only your JEE Main marks and rank matter. CBSE board exam marks are not considered in seat allotment for most engineering colleges like NITs, IIITs, and GFTIs. However, you must pass your board exams to be eligible for admission. Some private colleges or state-level admissions may consider board marks, but JoSAA strictly uses JEE Main scores for counseling and seat allocation. So focus mainly on your JEE Main rank during JoSAA counseling.