Your question is anything but clear but seems to be questioning the behaviour of Microsoft Commerce Server 2009. In which case it would make sense to direct the question to the vendor -
Microsoft Support[
^]
In my own experience of similar systems the order number is allocated on selecting "New Order" but if the order is not progressed then that number is discarded (in the same way that IDENTITY columns in SQL server work), so you would expect gaps in the sequence.
It would be a simple case to put a specific test through to prove/disprove this theory.
Probably your best bet to prove this is to turn on tracing for this area -
How to Trace Commerce Server Events[
^]. Once you observe the behaviours you are concerned about then capture and examine the log. I also advise you to turn tracing off as soon as possible afterwards as it usually impacts on performance.