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 = the average length of the extruded geometry (version 1.2 and newer). For old versions of Quantifier Pro, Length = length of the Profile Member extrusion path. In older versions, the length calculation would lose accuracy if the profile had x and y offsets but the newer method fixed that issue.
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). In version 1.2 and newer, holes and openings area will be deducted from the overall area IF the profile shape resembles a rectangular wall.
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.