The selection process for deletion is the same used in the new cloud construction operation described in detail here.
The auto filter will select data within a proximity to the selected surfaces. The one thing to keep in mind is that what is selected will be deleted.
Cloud Points Filtered to Selected Surface Faces
This option works the same except that it allows selection of individual faces from a larger surface.
Cloud Points Filtered to All Faces
This command also works the same except that all surfaces in the job file will be considered for the filter process and no surface selection is necessary.