Pritam I am sorry to say that you are not eligible for IIST admission because although the whole counselling procedure of IIST is based on the marks obtained by you in JEE Advanced examination but the eligibility criteria in the academic qualification is– Candidates must have passed Class 12 or any other equivalent examination with at least 75% aggregate (65% for candidates belonging to Scheduled Caste (SC), Scheduled Tribe (ST) and Persons with Disability (PWD) category).

With your 70.6% in 12th board exam even with the OBC category quota you are not eligible for the further processing and even if you get very good marks in JEE Advanced you will be also disqualified from the both JEE Advanced and JEE Mains counselling because of the minimum percentage you needed to be eligible for JEE Mains exam is 75% and without clearing JEE Mains you are never eligible for JEE Advanced.

The only chance for you to sit for the counselling is if you are in the 20 percentile of the students who have giver 12th board exam in your Gujrat board. Please check it out asap otherwise you will need to start searching the private colleges who give admission via JEE Mains marks.

Feel free to ask if you have any more queries. All the best!!