Unless the backup on the internal disk is older and contains files that you don't have elsewhere anymore, it doesn't do much for you other than enabling quick recovery of a file you deleted too quick. If the internal disk goes down, the backup on it will not help.
If the backup on your external disk is accessible and usable, you can delete the one on the internal disk.
If you want to keep it anyway but free up space on the internal disk, you can also first move it manually to the external disk.
If for some reason you don't mind leaving it on the internal disk but want it to not take up space on the external disk, you can exclude it in TM from being backed up. Of course, this makes sense only before the first initial backup, otherwise it's already on yur external disk.
I think what you're seeing are local snapshots that Time Machine uses. That would account for the 'backups' shown on the Storage tab. Usually these backups are deleted in a weeks time - they're just a temporary repository that can be used to recover data.
See Pondoni's article about local snapshots here -->> http://pondini.org/TM/30.html.