The manufacturer of your laptop in BIOS Settings will indicate the Maximum vRAM you can assign to your APU IGPU.
Normally, in the past, the maximum amount of System Ram you can assign to your IGPU was 2GBs. With newer laptops it might be higher than 2GBs.
The amount you can assign in BIOS also takes into account the amount of System RAM installed. So with more SYSTEM RAM you should be able to assign, if your want in BIOS Settings, the maximum amount since you have 16 GB of SYSTEM RAM installed now.
But generally, Windows will automatically assign whatever amount of System Memory to your IGPU vRAM so that you can run games or apps as needed only even though in BIOS you might have the minimum default amount assigned of 512 MB.
NOTE: Adding more vRAM will make your IGPU to run more efficient and smoother.