John. first off, JEE Mains has no minimum aggregate criteria. The 75% minimum aggrgegate is for admission to NITs, IIITs, CFTIs and to be eligible for JEE Advanced which is the entrance examination for admisison to IITs. So, even if you score less than 75%, you are eligible for JEE Mains but admission to NITs, IIITs and CFTIs is difficult. Now how you fared in 11th is not considered for calculating the eligibility criteria for JEE Mains. What matters is your 12th. So let's say you fared poor in your 11th but managed to score real good in 2020, like an aggregate of 75%, not only are you eligible for JEE Advanced, but you are also eligible for admission to NITs, IIITs, and CFTIs. So do not worry a bout your performance in the 11th. If you are afraid you might fare poor, concentrate on 12th to secure the minimum aggregate.