This is probly been covered a million times but I missed it and im new to the high tech electronics. Im wondering how to use the water level offset function. My home lake grenada fluctuates alot and im hoping this will help me out. How exactly do I figure the offset? Say for instance rite now our full pool is listed at 215.00 and water level is 202.40 so its 12.6 foot below full pool. Would I just set the offset to -12 and roll on?