If a candidate has passed his/her Class XII (or equivalent) in 2018 and wishes to improve his/her aggregate marks to meet the aggregate marks of 75% (or 65% for SC, ST and PwD) criterion, he/she can reappear for any number of subjects he/she wishes for improvement.  The percentage marks in this situation will be calculated by considering the marks obtained in 2018 or 2019, whichever is higher, in the respective subjects, in his/her two attempts in 2018 and 2019.   

Either they can submit class 12 results of 2018 or 2019 . Not both on the time of counseling they can't submit both certificate .

please don t spread falls news,if not knowing.you people just can misguide .
and above one is copied from jee advance brochure .so you can choose the subject which is higher in any respective year.