The numbers on the Rocky are just that. One persons Rocky may display 3 when the blades touch (true zero) and someone else -5.
You probably need to find that point first before the numbers mean anything to someone on this forum.
On my Rocky I find that 6 above the true zero point is about right for most beans in a double basket.
Flow rate is determined by the grind size and dose. The finer the grind and higher the dose the slower the flow. Courser grind and lower dose the slower the flow.
Hope this helps