Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Minimum
FIELDLAYER_CLAMP_MIN_VALUE
Parameter: Clamp Min
FIELDLAYER_CLAMP_MIN_ENABLED
Parameter: Maximum
FIELDLAYER_CLAMP_MAX_VALUE
Parameter: Clamp Max
FIELDLAYER_CLAMP_MAX_ENABLED