I suggest a better line of computation
around 38K people give MAT. So Per MAT, there are 4 99.99 Percentilers. 4 MATs have been considered for JBIMS(Sept-Dec-Feb-May) admission. Roughly 2 out of 4 people in top Percentiles apply for JB. So there should be around 8 99.99%ilers genuinely in race(This includes those ppl who forgot to fill JB forms, or didn't do it coz of ARC hassles, or are not interested in JB, coz they got the IIMs or other ivy instis)
This was for MAT alone. Consider 4 for ATMA as well and 2 for MHCET(OMS) ! and then half it. So U haf 3 more
8+3=11 Candidates, on 99.99 and seriously vying JBIMS!
Same for 99.98 and 99.97
Makes 33 Students on 99.97,99.98 and 99.99 who are vying JBIMS, all over INDIA(Not just on PG).Substract from this 5-6 people who have got percentiles overlaps..like same guy/gal

having 99.98 in ATMA, and 99.99 in MAT. makes a final 27 Odd people!
Number of Seats is 18.
So roughly only these students on these 3 Percentiles(97,98,99), would make it to JB(Unless a lot of people really screw up their GDPI's, haf exceptionally less work-ex+par marks: probability of which is very very less)
I would not stick my neck out too far, and would just say that If U R a 99.90-99.97%ile%iler, U need to have an absolutely awesome GDPI, Good Work-Ex+Par marks and an absolutely phenomenal luck, to make it to the elusive 18, in OMS!
All the best to every1!
Cheers