A mystery Update disk
Why does my MacBook Pro now show an Update disk when there isn’t one?
Disks or volumes shown in Finder match those in the hidden Volumes folder, but this shows a stray Recovery volume.
The Update volume is normally on your startup disk, hidden from view by being mounted not in the main Volumes folder, but in System > Volumes, alongside others such as FieldService that’s used by service technicians. It’s believed to be used by macOS updates to store their files during an update, and they should only keep a few MB of data once updating has completed.