I just got a bow drawing machine from Apple Archery. It is the one that you can use a scale with. Question: Why, when I use the scale does the reading come up 4-5 pounds lighter than the traditional way of checking draw weight? I even turned the scale upside down and tried it that way - no change. I also tried moving the rollers around to change where the bow is held - no change again. The bow is centered and the pulling point is always where the string loop is located. So, any ideas? Thanks!