Auto increment field works only if AllowNulls is set to False. Then it should use the database’s numbers after saving. So the number you see might not be the final number, it may change after saving (e.g. if somebody else picked up your number).
Generally I would not recommend to use this as using numbers for unique identifiers brings terrible problems (e.g. not knowing the final number until you save).
thank you for the explanation of the idea behind this feature. So then it is not a bug.
My use case is to generate unique identifiers (numbers) for service operations. We have a list of service operations and each operation has its code. It is a sequence of numbers. Now, the numbers has certain “inner logic” which is not needed anymore. So the idea is to generate unique number for any new service operation inserted into the list.
So I won’t use this feature and I will use GenerateSerial function, probably in the State workflow whenever new record is created.