Does anyone know what does the (ATC) beside the waypoint in the star chart means?
Good question. According to the NZ AIP it means "ATC Restriction". Make of that what you will. It seems superfluous in that the maximum speed is what it is published to be regardless. The speed restrictions in this case would seem to be more restrictive than generic airspace or holding restricitions and so I interpret this note to mean "this is the local ATC default maximum speed and is more restrictive than standard". Also, what McHale said. But I don't know for sure.