Someone please explain what this is supposed to mean?

ignore the guy above...., it seems that atc is not likely to give you runway 13 to land, most they can do for you is just to let you shoot a visual approach on 13, but circle to land on 31, it maybe for safety reasons, eg. aircraft doing pattern work, or others landing/taking-off or shooting an approach on 31, same exact thing happens in the real flying world...