I have the non touch. Have to be on the PAGE you wish to change, not the Screen. Each page requires a set up.
Go to data overlay, add, highlight the temp and then zoom in or out. Hit save when done. You should be good for that screen.
With the v4 upgrade, press the power key..your menu items appear..now
touch Edit Data Overlay..now touch Configure..then touch Size and you
will see your choices. Press Save after making your choice.