Not sure that I fully understand your question about design vs actual unless you mean pump data plate vs actual. However, each flow valve will provide x gpm at Y pressure. Valve characteristics are different so you need to have the mfr.s flow chart for that valve to determine flow. Some valves have ports on each side of the valve to determine delta-p, get your delta-p and check printed literature. Not sure if that answers your question.
Politicians need to changed like diapers, and for the same reason.
(read it somewhere)