For the last two years along with this year, the criterion of minimum marks was taken off, and it was mentioned that the student need to pass their BSc course to be eligible for the admission in IIT's/NIT's/CFTI's. Now as the condition is improving day by day, from  next year, the minimum eligibility criteria may again be made effective.

So you should try to score above 55% or 6.0 CGPA in order to be eligible for the examination. The score of degree is only required for eligibility and there is no influence of that score for admission. The admission to the course will be entirely on the basis of IIT JAM merit score.

For more information regarding IIT JAM consider the link below:

https://university.careers360.com/articles/jam-programmes

I hope this helps. Wish you a great day!