Previously, we can count the number of candidates who have scored ranks from the centre, by looking at the initial digits of the roll numbers
Say 712xxxx is from Kerala
514xxxx is from UP etc….
In that way we used to calculate the availabity of a seat in one particular state (depends on the number of candidates to have scored ranks)
But for the past few years, it is not the case
For the past few years, the seating is NOT arranged roll number wise
The number before you may be in another centre or another city even
you could have seen this if you had seen the seating arrangements in the list they had pasted at each centre (regarding hall arrangements) if was obvious