Voltage displayed

I am curious about the voltage readings I see displayed on EFIS. On initial power up, I see 12 point something, which I interpret as battery voltage. With the engine running, I see 14 point something, which I interpret as alternator output. On shutdown, when I select the master switch off and the display starts its 30 second countdown, the EFIS displays 3 point something but there is a boxed annunciation of On Battery 12 point something volts. What does the 3 point something represent? I hope it is not backup battery voltage.

The ~3V it is still your main volts, Backup battery volts is what you read on the annunciator message when the EFIS is on backup battery.