sounds like its giving you a total for soil and water which would be run off, stinky says check at run off,water you plants and dip the tab into the run off. by what you are explaining , you can check it b4 watering with that kit if you wanted to and adjust accordingly to get the right run off ph.which actually sounds to me like the right way to do it .
i dont know how accurate the soil part would be.i just bought a ph pen. measure run off. adjust accordingly. done

speedy