Room Boundaries - Elements appearing more than once per room

I am a bit confused , I am using the Room.Boundaries from both clockwork and arch-lab and getting some walls twice as the boundaries of the same room, how come ?
BTW here is a screenshot of testing done with the Revit RAC_Basic sample project .
Thanks for any help , Jonathan

Boundaries produce the faces of the room geometry. Multiple faces may be bound by the same wall. You can easily filter that list to the unique list of elements if you want to.


thanks Nick