This happens when the user first types an invalid name for the new ProDOS disk, then makes a correction to it. Here's the scenario:
1. The user puts the AFE disk in the Macintosh's external drive, and starts the program.
2. User ejects the startup disk from the internal drive, via the appropriate clicks on the Drive and Eject buttons, then replaces it with a blank unformatted disk.
3. AFE tells the user that it can't read the disk, and asks if the user wants to initialize it.
4. User selects 800K, ProDOS format, and clicks Initialize.
5. AFE initializes the disk and asks the user to name it.
6. The user accidentally types a name that is too long for ProDOS (or uses illegal characters).
7. AFE ejects the newly-formatted ProDOS disk and asks for the startup disk back.
8. The user inserts the startup disk, and AFE displays an alert about an invalid ProDOS name.
9. The user clicks OK, and sees a dialog box containing a suggested (valid) name.
0. The user makes minor changes to the name, but keeps it a legal ProDOS name, and click OK, expecting AFE to eject the startup disk and ask for the newly-formatted ProDOS disk back to record the new name.
Seconds later, the user has a hybrid disk: part Macintosh startup disk, and part ProDOS volume name -- AFE didn't let the user swap disks one last time.