I used to have a 696 (same tank). I don't recall where those two go, but I have owned several other Monsters, and they each had two vent hoses. I can tell you what they do on these Monsters.
One of them vents the cap area--if you overfill the tank (obviously, with the cap open) this one will vent that excess fuel and fumes overboard.
When the cap is closed, the other one vents the actual tank--if the fuel expands due to engine heat, for instance, this vent will allow the excess fuel/fumes overboard.
So I would get some more line and run both to either a small catch bottle, or route both somewhere such that any fuel vented will end up somewhere safe (not on the engine/exhaust, or on a tire).