I posted earlier but the term in Subject was wrong, and let me try again.

In Excel chart Y axis, I created a format code. Some are by mistakes, and I
want to delete them. I don't see any option beside Add there. How could I
delete those unwanted format codes?

According to Help (F1), I am supposed to be able to delete them from
Dialogue box launcher for Number. I opened and select Custom but there aren't
any format codes I created.

Thx for your help.