Having a problem with the way recuring invoices generates the invoice numbers

MOD

Having a problem with the way recuring invoices generates the invoice numbers - is there a way to set this as at the moment it seems to be auto generating all of my auto invoices with the same number/words and adding a 1/2/3 to the end - BUTit also includes all my clients initials as this is how I set up my manual invoices. ie. 12345 _ABC

So on recuring invoices i now get 12345 _ABC01
12345_ABC02
regardless of it is an invoice for ABC or DEF.

Is there are best practie way to do these numbers so it's not confusing for me or for my clients who are now seeing each others names appear on thier invoices!?

Thanks