Why are some page filenames appended with digabit####?

In earlier iterations of Documoto ("Classic"), publishers had the option to supersede a part in only specific books. 

Note: in Documoto Rocket, all part supersessions are global 
(e.g. the part is superseded in every book the part is 
included in) 

However, in order to support the partial supersession, Documoto Classic had to create a copy of the page the part was included on, resulting in two pages:

1. A new page where the supersession was performed (includes the new part number)
2. The original page where the supersession was not performed (retaining the original part number) 

To keep the pages unique, Documoto Classic appended the filename with digabit####.

Going forward, page filenames cannot be appended with 
digabit####