Available Drive Space = Capacity, but 60% is listed as used?

I have a Mac Studio (Max) with 1TB of storage space. (Running macOs Monterey)

A few days ago I noticed that when I click Get Info on my Drive, it says

Capacity: 994.66 GB

Available: 994.6 GB (668 purgeable)

Used: 667.49 GB

I'm only a math minor, but these don't seem to add up quite right.

When I click on About this Mac -> Storage, it takes a bit to calculate, but then shows a graph which has 119 GB of Documents, and 96GB of Apps. But it also says 1.02 TB available of 994.66 GB.

I use iStat Menus and I can actually see the graph drop from 50-60% usage to virtually nothing a few days ago... which was the day when I realized Adobe After Effects had 300GB of cache files. I told After Effects to empty the cache, and now it appears that everything is kind of messed up.

I've run a Disk Utility Repair on Macintosh HD, as well as the individual volumes. I've emptied the trash, and I've rebooted a few times. I even updated my system to 12.6.3 (Not willing to move to Ventura yet.)

How worried should I be about this? What other troubleshooting steps should I take?