1. Here's why
If you are using Windows 7 and your graphics card has got more than 4 GB memory, please ignore the memory read-out in the Performance Monitor.
The reason is that on Windows 7, DirectX cannot retrieve the correct Graphics Card Memory parameter for graphics cards with more than 4 GB memory.
Since Lumion relies on the DirectX memory parameter for the Performance Monitor in the top right corner, you'll also notice that the memory reading in Lumion will be incorrect.
However, this is purely a cosmetic error: all of the Graphics Card Memory is used in Lumion 6.5 and newer (in addition to all available System Memory and Virtual Memory).
Microsoft fixed this DirectX error in Windows 10, and we recommend upgrading to this version of Windows as soon as possible.