Question 2 GB ram but only read 500MB on Task manager

Since your motherboard supports integrated graphics, it will be reserving ram for that use.
It may also reserve ram for hardware i/o buffers.
In the bios, you should be able to adjust the amount of ram to be reserved for video.

Despite the mixing, I think you are ok.
If you want,
Run memtest86 or memtest86+
They boot from a usb stick and do not use windows.
You can download them here:
If you can run a full pass with NO errors, your ram should be ok.

Running several more passes will sometimes uncover an issue, but it takes more time.
Probably not worth it unless you really suspect a ram issue.
 
Just tried playing with combination of RAM and slots just like @punkncat suggested. Here is the result:

I have 2 RAM - I'll called it RAM 1 and RAM 2 (Mixed brand both PC6400)
The mobo has 2 slots yellow and black -I'll called it slot Y and slot B. The yellow one is the closer to the processor

Put RAM 1 to Slot Y -> Run, read 2Gb
Put RAM 1 to Slot B -> Run, read 2Gb

Put RAM 2 to Slot Y -> Failed to boot
Put RAM 2 to Slot B -> Run, read 2Gb

Put RAM 1 to Slot Y and RAM 2 to Slot B -> Run, read 2.5Gb
Put RAM 1 to Slot B and RAM 2 to Slot Y -> Run, read 2Gb

Actually I have another RAM that the label has PC5300 and from the same brand as RAM 1, but cpuz read the different brand and actually on PC6400. And got exactly the same result as RAM 2

It seems that the issue is on the mobo right ? but why it only effect RAM 2 and RAM 3


Thanks for the reply and solution 👍

Wil tried to run the memtest86 if it's not taken much time - or just tried to buy the same RAM as RAM 1 😀

One more thing - I don't think I found a config for memory allocation to the iGPU - I'm using vga card btw