Quoting this Quora article:
Installed RAM is the actual physical memory installed in your PC.
5.88 usable = Let’s just round this to 6GB for simplicity
8GB - 6GB = 2GB. This means that 2GB is being allocated by your system to the SHARED video of your Ryzen 3200U. This Ryzen processor DOES NOT have a discrete video card, this means that it HAS TO USE (or borrows) from the actual physical memory.
There is nothing wrong with your system, your memory or the laptop. This is exactly is what to be expected with a “U” processor. If you purchased a laptop with an “H” processor, then it would generally have a dedicated Vega graphics and will not use up any of the system RAM.
Unfortunately, there is no workaround for this. It HAS to use your memory otherwise it will not run at all. It does not matter if you bought an AMD PC or an INTEL PC. If the processor of choice has a “SHARED” graphics chip, then it will still use the system RAM and allocate it as VRAM (video memory).
If you look at the “build your own” section of the E4595, you would see optional configurations like 12GB or 16GB of system RAM, by choosing those you would have ended with at least 10 or 14GB of RAM leftover. 6GB is still not bad. It is still very functional for an entry level laptop especially if you do not expect a lot from your system. General web browsing, some apps, media playback should not be too much affected. You may not be able to open too many tabs on your browser or you may not be able to multitask too much but as long as you are mindful of this, your machine should still function adequately.
You could possibly return your laptop if you want more memory as I am quiet sure you would be voiding the warranty if you opened it up and installed additional modules yourself. You can then opt for a higher memory configuration or an H processor instead.
You could also look at the documentation that came with your machine, you MAY be able to reduce the amount of system RAM by setting it to MIN instead of 2GB, that way, it will only use up what is needed. There may be settings like MIN, 256MB, 512MB, 1GB and 2GB. This generally works for most PCs. Even if the only option on your BIOS is 1GB, then that will allow you to reclaim an extra 1024MB of RAM for system memory.
I hope it is clear, if not, comment.