Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Offset
GV_VECT2MATRIX_OFF
Parameter: V1
GV_VECT2MATRIX_V1
Parameter: V2
GV_VECT2MATRIX_V2
Parameter: V3
GV_VECT2MATRIX_V3
Parameter: Matrix
GV_VECT2MATRIX_OUT