Pretty common and the gauge is not terribly accurate, its just more of a reference.
Basically when the bike is parked on the side stand its leaning left; the fuel float is located on the right side of the tank, so when you stand the bike upright the fuel levels, the float raises and the fuel gauge registers more fuel in the tank.
This however can take a couple minutes to adjust completely.
Pretty sure this is what you are seeing.
2008 Versys 650
Been riding 8 or 9 years, and have owned 8 or 9 bikes; its an addiction I can't quit...