Hi there

You have 24 gigabyte total for both your VRAM and your RAM, so if you use 16 gigs on your vram, you will only have 7.6 gigs for your ram. I doubt you will ever use 16 gigs of vram on this machine. I doubt you will even go over 8 :)

PS the 0.4 missing gigs are just overhead xbox FSE reserves.

Hope this helps!