GITAM GAT 2020 rank cannot be predicted since the 'marks vs rank' changes every year with the change in difficulty of the paper, and, the no.of students appearing for it.
Analysing the previous year data, it can be said that with 64 marks, you have fair chances of getting CSE in Gitam University. You don't need to worry much, give it a try.
You can use our college predictor:
Engineering College Predictors 2020 - Predict your Admission Chances
Engineering College Predictors – Know your College Admission Chances Based on your Rank/Percentile, Home State, Caste, Gender, Exam Result & ...
Hope this answer helps you.