Catalina Update Fail Purgeable Storage
The purgeable storage is stored in a local snapshot. Apparently you can use the tmutil in terminal to delete these. Not sure how exactly but will update later today after speaking with the genius who fixed my mac.

Update:
This is what was explained to me:


List IDs of local snapshots: tmutil listlocalsnapshots /Volumes
Delete local snapshots: tmutil deletelocalsnapshots [date part of ID]
Repeat for all snapshots.


Haven't tested so try at your own risk. Let me know if it works. Worked for me but wasn't there went the steps were preformed.