Currently, Lansweeper does not scan VRAM that is above 4GB. This is because at this moment Lansweeper scans this from Win32_VideoController, which has the data type uint32. This means that it is impossible to have a value larger than 4GB stored in it.
I will add this to the list of Windows scanning improvements as in the future more and more workstations will have dedicated GPUs with more than 4GB of VRAM.