Recently our POnumbering sequence "spntaneously" changed from 12000 series to a sequence starting in the 200's.    
Never had this problem before.
 
We reset the next PO # back. We were good for a day or two then, the number sequence jumped again.
 
I suspect that one of our users (erroneously)  forced a PO number when entering an order and that this started the next number sequnce to follow accordingly.   Is this how DBA works?    Can I turn of the option to override the system assignment of next PO #?
 
Thanks
 

I see. Thanks