Create a new surface defined by a flat platform (polyline) at the 842 level which is larger than the other surface and use that for the analysis.
Ignore cut volumes you only need to use the Fill results.
Mike Evans
Civil3D 2022 English
Windows 7 Professional 64-bit
Intel(R) Core(TM) i7-3820 CPU @ 3.60GHz (8 CPUs), ~4.0GHz With 32768MB RAM, AMD FirePro V4900, Dedicated Memory: 984 MB, Shared Memory: 814 MB