Greetings of the day Uday

There is no such criteria (minimum JEE marks) for admission in to SASTRA university. SASTRA university has a separate procedure through stream 1 and stream 2 .

Stream 1
70 percent seats of every branch are filled through stream 1 based on 12 th percentage ( 75 percent after normalisation ) + JEE mains score ( 25 percent )

For example
12 th percentage - 88 (CBSE) and JEE mains score is 80 .
Normalised percentage of board would be as follows
88 * 100/98.6 = 89.25
(Assuming percentage of topper is 98.6 )
Now 89.25 * 0.75 + 80 * 0.25 =86.94
This is your final score . AIR (SASTRA) is prepared based on this final score . There is a chance AIR up to 4000 .
If someone is a topper of board exam and his JEE mains score is 40 then final score would be 85 and AIR (SASTRA) would be above 5000 . It proves that there is no chance for JEE mains score below 40 in stream 1 .

Stream 2 .
30 percent seats of every branch are filled through stream 2 based on 12 th percentage .
There is very less chance for percentage below 95 in stream 2 .
I know your chances are less but your intermediate marks is good so you still stand a chance to get admission through stream 1.
I would recommend you to apply for SASTRA without any fear as I see a little possibility that you may get a seat there.

Hope this clears all your doubts!!

All the best for your future endeavours