Backup temp space

Last night I got the following error when my instance tried to do a full backup using rsync to my NAS. Any ideas? What temp space is the error referring to?

Temp space has 237895680 available, backup needs approx 340787200.
Traceback (most recent call last):
  File "management/", line 561, in <module>
  File "management/", line 279, in perform_backup
  File "/home/user/mailinabox/management/", line 123, in shell
ret = getattr(subprocess, method)(cmd_args, **kwargs)
  File "/usr/lib/python3.6/", line 311, in check_call
raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['/usr/bin/duplicity', 'incr', '--verbosity', 'warning', '--no-print-statistics', '--archive-dir', '/home/user-data/backup/cache', '--exclude', '/home/user-data/backup', '--volsize', '250', '--gpg-options', '--cipher-algo=AES256', '/home/user-data', 'rsync://', '--allow-source-mismatch', '--ssh-options= -i /root/.ssh/id_rsa_miab', '--rsync-options= -e "/usr/bin/ssh -oStrictHostKeyChecking=no -oBatchMode=yes -p 22 -i /root/.ssh/id_rsa_miab"']' returned non-zero exit status 35.

Free space on the VPS.

Many thanks! I’ll resize the root partition.