On S.50.06 Specification Management: Window 2 you can assign the TAG Number to the specification item. If Tag Number is specified, then the idents will be built as per the Ident Key for Rule.
Clicking the Build Idents button builds the ident codes based on the Ident Key for Rule if the Tag Number is specified. If the Tag Number is not assigned, then the Idents will be built as in S.80.01.
The Rule Based Ident Codes built can be reviewed on S.50.06 Specification Management: Window 3 - Spec Item Idents tab.