To start with, around 2,00,000 candidates appeared for the CAT exam. This means that for every percentile, there are about 2000 people.
Now, let's say that your percentile is 95, which implies that the 5 percentile is more than yours. In other words, approximately 10000 candidates have scored better than you in the CAT exam.
Suppose that 2000 candidates did not apply for MDI, which leaves us with 8000 candidates. Looking at your good scores in 10th, 12th, and graduation, you are better than at least 4000 candidates out of the remaining 8000.
So, the number of candidates left now is 4000. In comparison, IIMs and private/government colleges like SP Jain, FMS, etc., there are around 1500 and 1000 seats available, respectively, in the general category, taking BLACKIS seats into consideration.
Assuming that they all choose colleges other than MDI, the probable candidates left for MDI with profiles better than yours would be 4000-(1500+1000) = 1500. Now, the number of seats available in MDI is approximately 350.
Considering the average GDPI, the probability of your selection in MDI would be 350/1500 = .23333. So, you have a 23.3% chance of getting selected for MDI.