Define the calculation type
The first dialog that opens is "Choose calculation type" -dialog.

Ultimately there are two different alternatives for the calculation type:
Calculate volume from a triangulated boundary
Calculate volume against a LandXML surface (Preferred option)
Select the desired option by clicking the toggle button next to the option.
Calculate volume from a triangulated boundary
The first option creates a new triangulated network from defined area. This tool is useful to highligh in the very beginning the cut and fill area.
When site is being built, the information is no longer as informative. During the construction it is suggested to use the other calculation type.
Calculate volume against a LandXML surface
The second option is very useful when the work has begun on the site. Up-to-date information is being compared against the designed state or start state.
This option needs the surface in LandXML. So rather than creating a new TIN from the area, it uses the TIN from a LandXML file.