I am not completely sure what you mean but here is what I think could help:
The Intel HD chip always has 128mb dedicated to itself, but if it needs more RAM, then it is capable of pulling 4073mb of free system RAM. Its shared memory, so if the CPU is taking too much RAM then the amount of onboard graphics RAM decreases. There is no set allocation for CPU and the graphics chip "fight" over shared RAM constantly changing the allocation of video RAM available.
I am pretty sure if your PC has enough RAM, then the graphics chip will generally have 4gb, (4000mb,) of Video RAM. However, I don't think integrated graphics chips are powerful enough to utilize 4gb of RAM.