Before anything.. please note that you're looking at things that normal users will never see, or perhaps even care.
This is because the Duo does not have a real-time clock inside.
Everytime you power it on, it starts counting time from 0, which in POSIX systems means January 1 1970.
I guess those are leftovers for failed operations.
You can try to manually recover, of course.
the number suffix is to make sure the filename is unique.
when saving, the pedalboard folder name is converted into a valid path name and truncated, so it doesn't get unnecessarily long.
if a folder with that exact name already exists, it tries a random number until it finds one that is unique, and thus okay for use.