...
Occasionally, you may need to assign more than one number sequence to a single field for a number sequence. For example, if you have created more than one number sequence for invoices, then you can use a table Number Series Relation (table No. Series Relationships ) to associate all relevant series with a single number sequence code. You can then enter the code into the invoice number. If you assign a new invoice number at a later time, you will be able to choose between all the rows associated with the code.
...