I assume by cut-off for selection in JEE Mains you mean to get qualify for JEE Advanced examination. So according to last year for OBC category student was minimum 115 marks out of total 360 marks and atleast 10 marks in each subject.

For further more details you can check out this link: https://engineering.careers360.com/articles/jee-advanced-cutoff

Feel free to ask if you have any more queries. All the best!!