On the 2012 & 2013 boats, if the gauge reads 0% with a full bag you will just need to cycle the switch on and off until the bag gets down to empty. I know it’s a pain but it’s the only way.

If the gauge reads 100% with an empty bag, you can use Mike's trick or trip the breaker to the rear PDM. This is located in the engine compartment mounted on the port side wall. You can then turn the switch to empty and the gauge will run down but the pumps will not run.