Read the "How much graphics memory does my computer have?" in the Frequently Asked Questions for Intel® Graphics Memory on Windows® 10 . You should have about 2GB (or more) RAM assigned for graphics.
If your device supports 6gb, good. But your graphcis will use 2GB of system memory.
Look under "What is the maximum amount of graphics memory or video memory my computer can use?"
As for dedicated memory, it is controlled by the bios of your device and rarely will you see it go above 128MB. As they say, it is old school.
A surprise, I managed to dedicate 2gb of VRAM on my GPU (Regedit> HKEY_LOCAL_MACHINE> Software> Intel.) Create a new folder called GMM, Create a key with binary value (In my case 64BitsDWORQ.) And then customize the key name and put "MemoryDedicadedSize." And customize the value, I made the value 2048mb, and when restarting my machine, I already had 2GB of dedicated RAM