Quantities may be calculated differently depending on several factors. Below is a reference for how Quantifier Pro calculates each quantity type.
Standard Groups and Components: Length = maximum dimension of the Object's bounding box
Profile Members: Length = length of the Profile Member path
All Objects: Surface Area = Sum of all areas of the faces inside the Object (front side of face only)
Groups / Components: Area = projected area in the direction of the smallest bounding box dimension
Profile Members: Area = Length * (greatest of Profile Width, Profile Height)
When it is important to know the volume and weight of a particular object, make sure that the Object is modeled as a 'solid' object. In a solid object, each edge bounds exactly two faces.
Solid Groups / Components that contain no child Objects: Volume = volume of the solid (same as value calculated by SketchUp)
Solid Groups / Components with child Objects: Volume = volume the mesh (calculated by Quantifier Pro)
Profile Members: Volume = volume of the solid (if solid) OR area of the Profile multiplied by the length of the member (if not a solid)
Non-Solid Groups / Components: Volume = estimated volume of the mesh
The weight calculation will depend on the unit weight data assigned to the layer that the Object is associated with. The weight will be based on the unit weight multiplied by either the length, area or volume.
The cost calculation will depend on the cost data assigned to the Object. To view the cost calculation, use the Cost Inspector Tool from within the Quantifier.