The way valves are modeled in the fluids domains is that it translates a spool position (S port input) to an orifice opening size. The orifice then defines the pressure drop vs flow rate characteristics. So now the question is what you mean by "different percentages".
If it means that at X% opening, the flow rate would be X% of the flow rate at max orifice area position, under the same pressure drop: what you can do is to assume X% of full spool travel from fully closed position == X% open. Construct a spool position vector, say 0-5mm with 0.5mm increments. Then you play with the elements in the orifice opening area vector at each opening position so that it gives you X% of max flow rate.
If by X% opening you mean the spool moves X% of full travel from the fully closed position, then there is likely a missing piece of information here: what is the flow rate at X% open compared to fully open? Some reference data will help you to set the opening area table/array in this case.
