Within Revit there are six different options to choose from when drawing your walls.
Each option changes the floor area/volume of the spaces in a slightly different manner and should be accounted for depending on what analysis type is intended once within the Virtual Environment. The key point to note is that the area/volume value that is in Revit properties, this value will be replicated within the VE.
Image from Autodesk Revit: Properties dialogue – Dimensions
