Can't see the pic but depending on your system, the aux battery will continue to draw from the main battery until voltage set on split charge is met (usually ~12.6v). So if your aux needs charging, your main battery will continue to charge the aux even with the engine off. Your main battery will then show 12.6v at rest. The aux battery wont charge until main battery is over something like 13.5v. Make sure you are testing when everything is fully charged.