You are confusing a unique identifier with a record number. Old ISAM files and spreadsheets have record numbers, relational databases do not. An autonumber is used as a unique identifier for a row in a table. It has NO other meaning.
If you want to create your own recordnumber, you're in for some tricky code. You would need to reassign the record number any time some row was deleted in order to fill the gap. This is truely a waste of time and computing resources.