How to create two callouts with the same ID number in Isodraw

I am using IsoDraw 7.2

My customer requires the callouts to be the same ID and my IsoDraw gives me a popup warning saying:

"The ID is not unique Please change the ID."

I have several items such as washers that are the same part number and the ID's are labled 5a, 5b, 5c, 10a, 10b, 10c, etc...

If I try to change 5a to 5 and 5b to 5 then I get the popup warning.

Is there a way to change several callouts and have the callouts have the same ID?