The GPS V is showing which maps are loaded. In this example I have loaded some European City Select 5 map chunks, one Worldmap map chunk and my own custom made Tenerife map. Here you can toggle the display of each individual map chunk by highlighting the mapchunk and pressing . If you want to enable or disable whole map products or all map chunks in one go, press .
You can now disable all maps and enable only selected map products. This would be nice if you have several mapping products loaded for one area. In this example that is the case for the Tenerife island, since I loaded both Worldmap and my own Tenerife map for the island.
If you have loaded maps from more than three mapping products, you will only see three of them here (the menu window isn't bigger...). Enabling or disabling the other(s) can only be done individually.