Swapna,
I have an understanding that when certain processes run, a block of numbers (order number, system assigned material numbers) can be reserved for use. If a block of 20 is reserved and only 15 are used AND the next block of numbers has been reserved in another session, then the 5 unused numbers are discarded unused.
Another time that i have seen 1 or 2 doc # missed, is that if a an order id created, a number is assigned resulting in the message Order 45002345 is created. Then an update terminate has occured. The number is used, but it was not created in the final analysis, so not there. I was party to this in one shop, i figured it out when finally some said "I keep getting these express messages . . ." which was the system notifying of the terminate update -- I would hope this is not the problem, but I have seen it occur.
Regards
Althea