I`m not sure what you are asking.
If you have a total of 8Gb of ram fitted to your system.
Windows once loaded into system memory will take about 2Gb of the main system memory.
Leaving you with, or it should quote 6Gb of memory space free for other programs.
What you also forget is that overtime with windows applications you install sometimes auto start after windows has loaded, each one takes a chunk of memory space.
Where as when you do a fresh clean install of windows, it is windows that is using a part of the 8Gb of system memory as the OS is memory resident all of the time. As it stands that should be the case.
The more programs you install that want to auto run after windows has loaded will eat into what it currently quotes as free memory for other programs.
Use system information of windows to verify how much ram is physically installed.
Bellow will be what is in use by windows being loaded into system memory.
And it will state how many Gb of memory is free for other programs to use.
1.5Gb of memory used is about right as windows os resides in system memory.
At 83% of free system memory I see nothing wrong at all.