I took a look at some Graphics Information regarding different Graphics Adapters
Intel Graphics Media Accelerator (GMA) 950
NVIDIA GeForce 6600GT (Desktop)
So actually 9100M G does contain "Dedicated Memory" of 256MB taken from the Main System RAM.
Shared System Memory refers to the TurboCache Technology from Nvidia (ATi Calls it HyperMemory) to use System RAM for Graphics
I myself is not too sure that System Video Memory is but it seems it is Zero for old Cards (6600GT) and 64MB for new Graphics Adapters.