I Cannot Delete "Default Set" from Norton Online Backup

I go to Norton Online Backup (https://nobu.backup.com/session/new) and click "sign in." After I click "sign in," I am taken to the Window where I enter in my sign credentials, then click "sign in."

 

There, on the page "My Devices," a picture of a PC is shown and listed is:
(name)-PC: Default Set

 

This "Default Set" is using "40% of 2 GB," only leaving me only 60% of my 2GB.

 

Now, I had thought I deleted my "Default Set" by opening up 360, going to "Backups," then "Manage Backup Sets," and deleting that set after I had created a new set, because it would not allow me to delete a set unless I had at least two sets.

 

So I deleted the "Default Set" but it still remains online, taking up my 40% of my storage space. I cannot figure another way to delete it. It no longer appears in Norton 360 (on my PC), so I can't delete it from there, and there's no delete button or option to delete on the "My Devices" page at Norton Online Backup.

 

Surely there must be some way to delete this unwanted backup set? Any suggestions or help would be appreciated. :)