gentex 261 rear view mirror

Hi Everyone, I was able to get this to work thanks to all of your wiring details. I have two questions: 1. What is the button with the white dot for? This is the button to the left of the "onstar" button. I first thought to go between temp and compass direction as per below but not certain as I don't have a temp sensor. 2. mine has the single display (1 line not 2), but when you 1st power it up shows the degrees symbol with the "C" for Celsius and the "F" for Fahrenheit. Thing is there isn't enough room to display both. Others I have seen have a top line for compass and line underneath for temp. Wondering if I hooked up a temp sensor would this cut out the compass? If so I could hook up a switch, to go back and forth when wanted, correct???

found out #1 is the phone button, still not sure about #2, any ideas?

nobody has any idea?