That is correct, check with the manufacturer of the implement. Different implements have different ratings. My bush hog slasher says 540rpm but my finish mower says 1000 rpm. I have the L185 so I can go 540, 750, and 1000 rpm. I have not found any implements that use 750 rpm unless it is a pump of somekind for spraying. Actually, my spray pump says 1000 rpm but there might be different ones.
Always follow the manufacturers suggested speeds or you could do some real damage to your tractor, implement, and yourself if it self destructs!