Why is my Priv storage filled up with seeming "ghost data"?

I have removed many apps, cleared my Google Photos cache, all my media is stored on my SD card... And yet I still run out of space.

In my Storage Settings, the graph shows about half of the "total space" of 23.86GB being available.
All of the data being accounted for adds up to 11.42GB.
The "Available" space is shown as 531MB.

Where is my remaining 11.91GB of storage space? I can't find it locked up anywhere.

Thanks for the help!
Michael