Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Mirror
MDATA_PATTERNSELECTION_MIRROR_PATTERNParameter: Repeat Count
MDATA_PATTERNSELECTION_DISTRIBUTION_REPEATCOUNTParameter: Margin
MDATA_PATTERNSELECTION_DISTRIBUTION_MARGIN