Hi there edward, yes you have to do that with it, off the top of my head its the alpha gain that you have to set to -0.5, rarther than go into a legnthy explanation of the settings and stuff theres quite a few videos on you tube about rendering displacment maps, best off doing a search for them.

Oh and on Pixologics site theres also tutorials there too using the Displacment exproter and then setting in maya etc etc

Hope it helps