As I'm sure you know, the gauge includes all the water from OBJ, Daisey and the N. Fork of the Slate. In my experience, for OBJ, 500 equals low, 700 equals medium, 1000 equals high. Last weekend, the gauge was fluctuating between 700-800. Obviously, the flow rises significantly during the day when it is warm and sunny.
For Daisey and Slate, the more water the better. 700 on the Slate is probably the min for good flows, with evening runs best.