End Area Volume

Can anyone explain the following items and how they affect end area volumes?

  1. When you perform an "element information" on a feature definition there is a section named "Surface Defaults" and there are the following options.  I cannot find anything that explains what exactly these options do:
    1. None
    2. Existing
    3. Design
    4. Substrata
    5. Subgrade
  2. When in the End-Area Volumes dialog there is a tab named Classifications.  Once again I cannot find any information on the 6 different classifications that you can select.  What do these do?:
    1. Ignore
    2. Unclassified
    3. Unsuitable
    4. Rock
    5. Designed
    6. MDC

I have modeled existing pavement on my current job and have brought that surface into my cross sections.  In my state this existing pavement needs to be totally removed whether it is in cut or fill.  I would think that if I classified this as an "unsuitable" that the end-area volume tool would quantify this area and if it is below my proposed surface, it would fill the area that once was occupied by the existing pavement.  I simply cannot get the software to do this.

The unsuitable Materials by Station would be a useful tool if I were building a new road were there was not a road before.  However, just like the other 95% of our jobs, we are building a new road were an existing road is now.  I cannot keep a single width unsuitable from tie-down to tie-down because I need to remove topsoil and existing pavement which are at dissimilar depths (topsoil is 6 inches and pavement is 15 inches).