Question Why has the Usable RAM dropped from 14GB to 13.5GB ?

[Heoheo3]

Hello today i found i have 13.5GB RAM usable instead of 14GB like I used to have. My Integrated GPU uses only 2GB RAM so what's using the additonal 500MB ?

nd i had

 

[Aeacus]

so what's using the additonal 500MB ?

Pagefile.sys is one suspect.