Firstly, JBIMS doesn't offer an MBA course. Instead, it offers an MMS course, which is the same as an MBA. Second, there is no PGDM program at JBIMS.
JBIMS Mumbai only offers three full-time programs: the flagship MMS, which is affiliated with Mumbai University, and in-house MHRD (master's in human resources) and MSc Finance. The selection process for these in-house programs is different, and it includes a minimum score on the CAT or CET test and a GDPI.
Now, for the most popular course at JBIMS, the MMS, all you have to do is get the cut-off score. There are no other selection factors, so if you get the cut-off score, you'll be on the list. JBIMS now only accepts MAH-CET, CAT, and CMAT scores.
The cutoff is usually very high. The cutoff for students in the open category is between 99.9 and 99.8. 85% of the seats are held for students from Maharashtra, and the other 15% are for candidates from all over India. Since JBIMS is a government college, places are set aside for OBC, SC, and other groups.
To sum up, JBIMS doesn't have a GDPI selection process like the IIMs do. Instead, you just have to get the cutoff score and you'll get into the MMS course.