There are two main schools of opinion when it comes to dialing-in a skimmer Essphore. Those who prefer a "wet" skim, and those that prefer a "dry" skim.
To achieve either of these concentrations of skimmate, adjustments vary wildly from manufacturer to manufacturer. For example, I use a Deltec AP model, the settings on mine, would not suite say a coral life skimmer. It really is a case of tweaking air intakes and water feed until you are satisfied the settings are at an optimum. Sorry, I can't be more precise than that.