My guess is that it will all correct itself tomorrow. I think this is the same thing as I describe here http://community.rachio.com/t/display-bug/4719/3
It's the odd way that "today" displays. Once you set it to empty, it saw that the MAD was going to be below zero, so it said it needed to water. But the prediction for "today" doesn't take into account that the time to run your schedule has already passed. Very confusing right now, but take a look tomorrow morning. It will probably run.
If it doesn't water, it might be because you got some rain. Check the moisture level charts in the morning.