Well, since JEE advanced their is fix total marks so instead of number of marks the percentage of marks would be a better assumption

according to the past cut off

You have to score around 30% to be eligible for any of the branch offered by IIST thir.

But since this year paper would be subjective in nature

So you can expect a seat of any desired branch around 26-27% socring.

Ps - marks I've told is from the best of my knowledge. Since JEE advanced os unpredictable in nature so the orignal scoring may can vary.