lost vram? acer nitro 16

Been trying to optimise my acer nitro 16 with rtx4070 8gig and get somewhat different results each day,

Most notably was when I yesterday went in to play the last of us part 1, and it ran slightly worse than the other day, going to the menu I saw it showed around 7900mb vram for me to use but I can swear I saw it was up on 8100 the day before. I have been messing around a bit much lately but I just dont get what I could have done to bring it down by 200mb?