With no logo visible you will have 6w, when the voltage of the battery drops below (not sure exactly but something near) 11v the logo will blink. But still at full output.
It's not the clearest, but it works. Remember that the POW graph is a full range, so bars all the way to the right is 6w, so when in doubt look at the power out.
Tobias KK7BCO/2M0TFF