climate control on 89 park ave

Just wondering. on the electronic climate control on my 89 park ave (actually, this was the same on 2 '90 park aves that I've owned as well),
there is a "button" between the "high" fan control button and the external temp button. if you press there, the display shows "00".. Just wondering what it's for, if anything?
Also, does anyone know how to change the climate control from Celsius to Fahrenheit, and vice versa?
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