This issue has been previously discussed but never fixed.  In the web interface, under Advanced, VPN Client, Client List, Add, the window that appears displays a list of offline devices, many of which may be very old entries and no longer valid.  My list contains some 50 devices.  There is no way to delete the devices.  This list is saved during a backup and the moment one does a restore after a factory reset, the list reappears.

This list appears to be a different one than that used for Access Control.  I managed to get the access control list cleaned up but there is no way to edit the VPN devices list.  Deleting clients entries with the Tether app does not clear the entries in the VPN devices list.

Please add an option in the web interface to delete entries in the VPN devices list.