I looked it up..if I read it right it means counter rotation....meaning your prop turns counter clockwise I guess...I believe they use a counter rotation engine when a boat has a few engines hooked up..like some of the 3 and 4 engine boats you see for off shore fishing....
At one of the harbors down on cape cod..I seen a boat there with 4 Yamaha 250's on it...pretty nice setup.....rigged for tuna fishing...