The tree on top lists main windows in the DriveLine skins. Primary and Secondary.
The list contains a list of monitors connected to the PC. The star indicates the 'Primary' monitor as defined by windows.
When you click on a monitor in the list, it flashes that screen blue so you can be sure which monitor you're mapping to.
You didn't say which screen has the star next to it (VGA or HDMI) so I'll just make up a scenario.
So, let's say your HDMI has the star on it. But you want DriveLine to only show up on the VGA.
You should be able to set 'Primary' to which ever screen makes the VGA flash.
And set 'Secondary' to none. Since you don't want a secondary DriveLine window.