Having friends at ISB Hyderabad, I got to know that there is no such cut-off for ISB. 

• Firstly the interview panel checks your overall achievements starting from schooling till your graduation level, in the curricular and co-curricular field. 
• They examine your entire profile for your selection. Then you get shortlisted for further selection. 
• Many of them did not manage to get very high scores in the GRE but still, got selected. It is just because of their aptitude that is reflected in their profile. 
• It is easier for those who already served in the Indian army and then decided to enter ISB. It has been seen that they have already cracked the SSB exam so they must have higher values like integrity, patience, and discipline imbibed in their personality. 

Thus we can say that there is no particular cut-off, but for ISB, Hyderabad you are judged according to your entire profile.