Garmin G3X Touch Pilot's Manual page 77

Setting the selected altitude:
Turn the large Knob associated with the PFD to set the Selected Altitude in
100-ft increments.
Or:
1) Touch the Selected Altitude.
2) Enter the desired altitude using the keypad and touch Enter.
Syncing to the current altitude:
1) Touch the Selected Altitude.
2) Touch Set to Current and touch Enter.
'Set For Field' is only available when aircraft is on ground.
NOTE:
Selected Altitude Bug
Barometric Setting
190-02472-00 Rev. D
Altimeter
Garmin G3X Touch ™ Pilot's Guide for Certified Aircraft
Flight Instruments
Selected Altitude
55