The folders immediately inside the cur directory correspond with your clients. Each folder matches up to a single client ID from the Avamar Server. The folders inside the client directories are individual backup directories. Backup folders are named to match the create time of the backup.

In the second screenshot, the files shown there are probably from a VMware Image backup since the files are stored "raw", directly on the DD filesystem instead of being stored in a CDSF container.

If these files didn't have a corresponding Avamar backup, Avamar GC should have already cleaned them up. I would strongly recommend against deleting these manually unless you've confirmed (twice!) that the data does not correspond with any valid Avamar backup. If you delete files that Avamar is expecting to find, data integrity checks on the Avamar will fail.

If in doubt, I'd recommend working with the Avamar support team since they have the skills and expertise to map data between Avamar and DD.

Edit: Thinking about this some more, saying "data integrity checks on the Avamar will fail" doesn't really cover it. If the Avamar hfscheck is failing, that will prevent old checkpoints from expiring on both the Avamar and the DD and your capacity problems will get a whole lot worse.