Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Offset
MDATA_EXTRUDEINNER_OFFSETParameter: Offset Variation
MDATA_EXTRUDEINNER_VARIANCEParameter: Subdivision
MDATA_EXTRUDEINNER_SUBDIVISIONParameter: Create N-gons
MDATA_EXTRUDEINNER_CREATENGONSParameter: Preserve Groups
MDATA_EXTRUDEINNER_PRESERVEGROUPSParameter: Maximum Angle
MDATA_EXTRUDEINNER_ANGLE