Using 2010. Created backup of NAS. Editing backup does not show selected folders

I've created and run a set of backups of my NAS drive. All the backups worked - I look at the backups and see all the right files in them. But when I go to edit the settings for the backup, the list of files/folders to backup shows that it is set to backup C: - not the UNC path; so I can't figure out how to edit the list of folders I want backed up.

Is the backup going to work on schedule? Or is it really defaulting back to the C: drive? It's very confusing.