I see a lot of wrong answers already present to this question. God knows what their sources are!
Since I’m a student of VIT and have gone through the whole of the counselling process last year, I can provide you the correct information.
Firstly, VIT does not divide the students in different categories as per their ranks.
Secondly, the Category system is basically VIT’s answer to Management quota.
Actually VIT has fixed the number of seats in each of the 5 categories. There are roughly 200 seats in the 1st category and 100 in each of the other 4 categories in every branch. So as the students start taking admission, the seats start getting filled, starting from the first category seats, and then moving to the 2nd, 3rd, 4th, and 5th categories.
So you can end up getting CSE in the 5th category even with a rank of 10k while on the other hand, you may get Civil in the first category even with a rank of 30k.
Hope your doubts are cleared. Ping me for further queries.