Why does the percentage of memory usage in the column title not nearly match the result of the added memory usage in the column for the individual programs, but is always apparently much higher?
E.g.: How do 82% of RAM come together in the corresponding column name in the Task Manager, even though adding the memory usage of the individual programs in this column would obviously not come close to this 82%?
Memory leakage? Some (badly designed) programs do not release memory back to the OS after the program stops. The program is not running so you do not see it listed but it has tied memory up.
Why does the percentage of memory usage in the column title not nearly match the result of the added memory usage in the column for the individual programs, but is always apparently much higher?
Because memory is not used by programs only, it is also used by Windows and drivers, however those won't be shown in task manager.
If you run task manager as Administrator more stuff will be shown but still not all system use.
Bluetooth: TP Link 5.0 Nano USB adapter UB500
WLAN: D-Link 150 Pico USB adapter, N standard
Web camera: Logitech C270 HD 720p @30fps
Microphone: Trust MICO, model 23790
If it were only a small difference, I could understand it, but the difference is huge. This apparently also means that Win seems to constantly be using 8 - 10 GB of RAM, so there isn't enough left for the programs.
No, Resource Monitor is part of the operating system, there is no need to download anything: Open Resource Monitor in Windows 11 Tutorial
Note that Windows might reserve a portion of memory without using it, this is then shows are "used" but is in fact unused.
I suggest you to read "Pushing the limits of Windows memory" MSDN article to have a firm grasp of Windows memory.
Bluetooth: TP Link 5.0 Nano USB adapter UB500
WLAN: D-Link 150 Pico USB adapter, N standard
Web camera: Logitech C270 HD 720p @30fps
Microphone: Trust MICO, model 23790
Also put dxdiag in the Start, Run box to see what video is using, seems to always take some of the system RAM even with a video card with its own memory being used instead of the onboard adapter.