Hello Aspirant

The admission in SASTRA University is based upon two streams:

Stream 1: 75% marks of class 12 boards and 25% marks of JEE mains is considered for ranking.
70% of the seats get filled with this stream.
As your percentile I'm JEE Mains is less, your rank will get increased.

If your class 12th percentage is around 90-95% and 80% in JEE Mains then you have good chances to get into SASTRA University.

Stream 2: Your rank is calculated based upon your class 12 percentage only.

30% seats get filled with this stream.
Since the number of seats is less will this stream, the competition is very high. To get into SASTRA through this stream, you need more than 95% in your class 12th boards.

As your percentage in class 12 boards as well as in JEE Mains 2021 are good, so you have good chances to get into CSE branch from SASTRA University.

Hope this helps
All the best