The meter above the magnum Control is registering a negative number. It's been that way since we've owned the coach. We just recently put in new house batteries, it still registers a negative number.
What is the meter above the Magnum panel?
All 12v meters will read negative when connections are reversed: Meter positive to battery negative, etc. Reading is accurate, just don't pay attention to negative sign. Or swap wires.
Could also be "cumulative/total amps" and that feature needs to be reset. A negative number on that means more discharge than charging.
Again, depends on WHAT is reading a negative number.