The RJ60 has a button that will give you a fairly accurate salt reading. It also has "dummy" lights for salt too low or too high. As long as these lights are not on, your SWG is happy. It is better to be in the middle to high range of salinity at the beginning of the season to avoid being too low for splash out or rain drains. The unit produces more CL2 with a higher salt percentage up until the point where the unit could damage the power supply, which is why it alerts for salt too high.