[ORD] Cut and Fill volumes calculation - parameters and Volumes Option

Hi everybody,
we can use Civil Analysis/Cut and Fill Volumes command.
That's great. But I can guess only how calculations are done. Some parameters are a little bit unclear because this chapter is unfortunately completely missing in ORD documentation. I can combine more parameters but how is program solving this combinations, is in stars. I have seen more videos and thanks for video here. Because volumes is one of most important thing in our projects I would like to know more details.

And my questions
- What happens when I use parameters (Compute Unsuitable, Compute Custom, Compute Substrata) in calculation dialog?
- How does program work with different types of terrains and meshes, which can have specific type for volumes calculation. How these types affect the calculation? What does it mean Custom, Unsuitable, Subgradem, Substrata in volume calculations? Note: TERRAIN can have these Volumes Option types for calculation (Design, Existing, None, Subgrade, Substrata) in Feature Definition, MESH can have these Volumes Option (Design, Existing, None, Subgrade, Substrata, Cut, Fill, Unsuitable, Custom) in FD setting.

Can somebody explain it?

OpenRoads version 10.08.01.33

Josef