Dxdiag Showing MORE Video Memory than i have

[Low end PC Gamer]

As the title says that's the problem. well obviously its a good thing but I want to know how could that happen. Shared from pagefile or RAM ??
I have a 1GB GTX750 GPU but dxdiag shows I have 3GB of video memory.

 

[k1114]

If you click the save all info at the bottom and open the txt file, it breaks it down. But ever since vista, windows has a shared amount from ram. This does not take away from ram as it can be used by both.