So I have a backup partition set aside on my 100GB HDD (old computer) of about 30 GB. I have some files that I want both Windows and Ubuntu to access (a NTFS partition) as well as the backup directory for Ubuntu.
However, when it goes to automatically backup it says that there is no space left. I have my backup settings set to this:

and it says that old backups will be kept until backup location is low on space. Why isn't it deleting old backups if it doesn't have enough space? Is it too low in the backup directory (again, delete old backups) or is it a problem with my /tmp or ~/.cache?
I looked at this question: Why does Déjà Dup say there is no space left?, but that didn't help any. AFAIK my tmp folder and my .cache folder aren't too large:

EDIT: (11/18/2013)
Added results from command (duplicity remove-all-but-n-full 1 file:///media/nate/Backup/Backup --force):
Synchronizing remote metadata to local cache...
Copying duplicity-full-signatures.20130901T193629Z.sigtar.gz to local cache.
Copying duplicity-full.20130901T193629Z.manifest to local cache.
Copying duplicity-inc.20130901T193629Z.to.20130905T184555Z.manifest to local cache.
Copying duplicity-inc.20130905T184555Z.to.20130912T120237Z.manifest to local cache.
Copying duplicity-inc.20130912T120237Z.to.20130919T173913Z.manifest to local cache.
Copying duplicity-inc.20130919T173913Z.to.20130926T110023Z.manifest to local cache.
Copying duplicity-inc.20130926T110023Z.to.20131003T111040Z.manifest to local cache.
Copying duplicity-inc.20131003T111040Z.to.20131010T112231Z.manifest to local cache.
Copying duplicity-inc.20131010T112231Z.to.20131019T172556Z.manifest to local cache.
Copying duplicity-inc.20131019T172556Z.to.20131024T120102Z.manifest to local cache.
Copying duplicity-new-signatures.20130901T193629Z.to.20130905T184555Z.sigtar.gz to local cache.
Copying duplicity-new-signatures.20130905T184555Z.to.20130912T120237Z.sigtar.gz to local cache.
Copying duplicity-new-signatures.20130912T120237Z.to.20130919T173913Z.sigtar.gz to local cache.
Copying duplicity-new-signatures.20130919T173913Z.to.20130926T110023Z.sigtar.gz to local cache.
Copying duplicity-new-signatures.20130926T110023Z.to.20131003T111040Z.sigtar.gz to local cache.
Copying duplicity-new-signatures.20131003T111040Z.to.20131010T112231Z.sigtar.gz to local cache.
Copying duplicity-new-signatures.20131010T112231Z.to.20131019T172556Z.sigtar.gz to local cache.
Copying duplicity-new-signatures.20131019T172556Z.to.20131024T120102Z.sigtar.gz to local cache.
Last full backup date: Sun Sep 1 15:36:29 2013
No old backup sets found, nothing deleted.
EDIT: (11/19/2013)
Ran duplicity cleanup file:///media/nate/Backup/Backup --force
Local and Remote metadata are synchronized, no sync needed.
Last full backup date: Sun Sep 1 15:36:29 2013
GnuPG passphrase:
No extraneous files found, nothing deleted in cleanup.