how many marks eligible for CLAT selection

Hey
The marks required for admission in the  NLUs differs each year due to several factors like the level of difficulty of the paper, level of competition and much more. In the previous years, some year the marks required for top 5 NLUs were more than 120 and in some year it was more than 140. In some year 100+ marks were required for admission to any NLU, and the next year it was totally different. So it varies accordingly, and an accurate estimate can't be made for this. So what you can focus on now is to practice as many papers as you can. Try to time it while you're practising too which will help you to learn how to manage your time in the exam hall. Focus a lot on the Current affairs section and the legal awareness section. Practice the part you're weak in. Stay focused and healthy.
But you can get a fair idea of rank required from previous year trends.

Here is a list of NLUs and their respective cut offs for the general category for admission through CLAT in the previous year. You can expect a similar range of cut off ahead too.

National Law School of India University
66
National Academy of Legal Studies and Research
135
National Law Institute University
386
West Bengal National University of Judicial Sciences
260
National Law University Jodhpur
376
Hidayatullah National Law University
657
Gujarat National Law University
494
Ram Manohar Lohiya National Law University
668
Rajiv Gandhi National University of Law
924
Chanakya National Law University
1186
National University of Advanced Legal Studies
928
National Law University Odisha
1167
National University of Study and Research in Law
1255
National Law University and Judicial Academy
1556
Tamil Nadu National Law School
1571
Damodaram Sanjivayya National Law University
1432
Maharashtra National Law University, Mumbai
503
Maharashtra National Law University, Nagpur
1532
Maharashtra National Law University, Aurangabad
1588

Best of luck!