That doesn’t include various amounts that are reserved.
For example there is some ram (2 GB default on systems with ≥64 GB ram, 4 GB with game mode on) that is reserved exclusively for the iGPU, which isn’t counted in that number (although the iGPU can access a lot more ram than just what is reserved for it, the reserved amount is just for improving compatibility with certain things).
Then there are usually a couple hundred megabytes reserved for reasons other than the iGPU.
Overall 91.8 GB seems around where I’d expect (a little high actually, I would’ve expected 91.6-91.7 GB) if you have game optimized mode on (which IMO is a terrible name barely related to what that feature does). If you have game optimized mode off it seems a bit low, but not necessarily out of the ordinary.
That is normal.
Memory training usually takes under 30 seconds, even with large amounts like 96 GB. However with DDR5 it has become a lot more common to see outliers that take as long as 20 minutes. Those outliers are still rare, but since it is such a long time you see people post online when it does happen.