It is important to note that there is not any category division such as 3A, 3B, etc in the JOSAA counseling procedures. Only the OBC term is considered for all.
One of my friends is studying at NIT Surathkal and he got around 140-150 marks in JEE Main, his rank was around 50k in CRL, and around 13k in the OBC category. He got a seat in NIT Surathkal in Chemical ranch in Special rounds of JOSAA Counselling. He had secured a percentile of around 95.5.
If you want to get into any branch of NIT Surathkal, then you should try to score a minimum of 95% in JEE Mains in being on the safer side. For that, at least 150+ marks should be scored. With this score, one can surely get into NIT Surathkal. If you want a circuit branch then they should try scoring more marks.