There is only 11.7GB on the HD. Time Machine claims it backed up 923.7GB. Why?

I set up a new 1TB M4 MacBook Pro because I mismanaged space on my 500GB one and I could not recover. I am trying to make sure to set it up properly, so One Drive and iCloud play nice together, and Time Machine backups happen daily.

What is Time Machine doing? Here is the situation:

1. Finder says my iCloud account has 2TB available, 656.1GB used, 71.1MB "on disk" (I assume that means downloaded).
2. Finder says my OneDrive account has 1TB available, 488.3TB used, and 175.9MB "downloaded" (I assume that means on disk).
3. Finder says Macintosh HD has 994.6GB capacity, 915.7GB available, and 11.7GB "Used" (I assume that means "on disk" or "downloaded". This makes sense to me.
4. After an initial set up 2 days ago, I formatted an external 1.02TB SSD as a Time Machine Backup, and performed the first back up, which showed up as "2025-12-18-141539" (15.6GB) Time Machine Backup"
5. I noticed it didn't perform a back up yesterday, so I went in today and asked it to perform one.
6. Strangely, it took several hours, and now that it is complete, opening the back up drive shows no backup for today (Dec 22).
7. Still, Get Info on the External SSD claims 923.7GB used and 100.GB available. Below is a snapshot from during this backup process, overlaid with a "Get Info" on the HD.
8. What the heck is going on?

[Re-Titled by Moderator]

Original Title: There's 111.7 GB on my 1TB M4 MacBook Pro. Why does Time Machine claim it backed up 923.7GB?