As you said there is no devices attached to those nodes. They are ghosted nodes. They should have been showing in a similar way on the C7, maybe you just never noticed? They are either from a device you force removed from the devices page, or failed z-wave pairings.
There is an entire guide on the forums on how to remove them. How To: Remove Z-Wave Ghosts using a UZB Stick
It was originally created for using USB stick but also has some tips for the remove process through the hub itself. Basically, click Refresh, wait, look for remove button, click remove (does not always work).
