Changing this assigns the minimum amount of RAM allocated for the GPU. Setting to 4GB is required for Guardians of the Galaxy and maybe other games.
In testing has also decreased stutter and increased overall in-game performance.
Red Dead Redemption 2 seems to do best with the setting at 2GB
This can always be changed back. In rare circumstances, this can have a negative impact for performance on games(for games that specifically demand more RAM than VRAM). In this instance you can change it back to the default value of 1G
Here is where you will change your core HW settings.
On the menu that appears choose "Setup Utility"
Advanced > UMA Frame buffer size
select 2G or 4G
press the [two squares] button next to the D-pad to exit and save changes.
Proceed to the next step 3. Windows OS Tweaks