ISBN Format
The “ISBN Format” setting (Admin > Management > Settings > Other) dictates the formatting of the ISBN in the Orders module (Admin > Sales > Orders).
Example:
It’s also used by the “ISBN (custom)” checkbox on the “Export” cart mechanism.
If you’d like it used elsewhere, open a support ticket.
By choosing a value other than “Standard”, the ISBN is no longer formatted according to the ISBN governing body’s guidelines.