Garmin G3X Pilot's Manual page 378

AFCS
4) As the aircraft nears the Selected Altitude, the flight director transitions to
Selected Altitude Capture Mode, indicated by the green 'ALTS' annunciation
flashing for up to 10 seconds.
At 50 feet from the Selected Altitude, the green 'ALT' annunciation flashes
for up to 10 seconds; the autopilot transitions to Altitude Hold Mode and
levels the aircraft.
3
Selected Altitude of 12,000 MSL
ALT Mode
4
KMKC
2
1
Departure
356
Garmin G3X Pilot's Guide 190-01115-00 Rev. K