It would suggest that while running the game, or any game in question that the system memory usage is more than 80%
And when you are dropping back to windows desktop windows it`s self is showing 12% usage for the OS it`s self as it it always memory resident Luke.
That windows is in fact using the page file, or a swap file on the local hard disk, and reloading some data from it.
So the main question is how much free system memory do you have left after windows OS is running and memory resident.
If you only had a maximum of 4Gb to 6Gb of system memory in total physically fitted to the system it would resort to the swap file depending on what game you were running.
8 GB of physical ram fitted to the system would leave about 5.5 Gb to 6 Gb free.
That is after the windows OS is loaded into main system memory and is always memory resident for the session or use of your system.
The thing is when a game quotes it`s system requirements, for example 8Gb of system memory it does not take into account what windows is using of the total physical ram fitted, and what it needs to run.
So in real terms most games that say minimum, or maximum mean even after windows has loaded into system memory or ram you should have 8 Gb free of memory available to run the game at its optimal settings.
A quick way is to simply open up system information of windows.
Because it will show you the total physical memory fitted then what the windows os has taken of it.
And last of all what is truly free for any other program or a game loaded into memory as a maximum that you have.
When you launch a game and for example when running it uses up to 6 Gb.
Because windows Os is always running behind it the memory utilisation can be as high as 88 %
And windows would automatically resort to swap filing or page filing mode from the HD.