When we attach DataGroup instance data to a MicroStation solid or surface, the values for the Volume and Area properties are represented as a zero quantity in the DataGroup schedule.
The key to adding these two values to any schedule would be to include two specifically named properties in the object schema:
1) A property with the name of “SurfaceArea” with an “Area Units” data type to report on the modeled objects Surface Area
2) A property with the name of “NetVolume” with a “Volume Units” data type to report on the modeled objects Net Volume, if available (not available on surface models)