Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Scale
SCALE_SCALEParameter: Variation
SCALE_VARParameter: X Scale
SCALE_XSCALEParameter: Y Scale
SCALE_YSCALEParameter: Z Scale
SCALE_ZSCALEParameter: Over Age
SCALE_OVERAGEParameter: Scale Gradient
SCALE_AGEGRADParameter: On
IN_SCALE_ONParameter: Animation Time
IN_SCALE_ATIME