A number of functions can calculate slopes down to a surface. These are for terrace surfaces - Fixed Slopes and Variable Slopes; and for terrain strings - Create Child and Range Edit.
These require you to specify the desired cut and fill slopes.
There are occasions where both a cut and a fill slope are possible options. For example in the sketch below, fill can be achieved on the left-hand side using either a fill slope of 1:2 or a cut slope of 1:3.
Specifying your requirement is achieved using the combobox selection of the above four functions labelled “When cut and fill are both possible”.
The available modes are
Default (Closest) - By default whichever is the closest of the cut or fill ground intersection is used.
Try cut before fill - First try get a ground intersection going upwards with the cut slope. If one is found then use this. (Note that this is still technically a fill scenario.) If one is not found then revert to going downwards with the fill slope.
Try fill before cut - First try get a ground intersection going downwards with the fill slope. If one is found then use this. (Note that this is still technically a cut scenario.) If one is not found then revert to going upwards with the cut slope.