Some objects on diagrams such as Clones can be cross referenced, so that you can see where the master of a Clone is and where Clones exist.
The XRef tab in the Project options controls whether and how they are displayed.
You can also display the page name rather than the page number for clones, and even truncate that to a selected number of letters.
Some of these settings, such as Show Clones can also be set for each diagram in the Diagram Details form
See also Defer Symbol Links display