Garmin G3X Pilot's Manual page 342

AFCS
• The Altitude Reference can be adjusted up or down in 10-foot
increments by pressing the FMS Joystick up or down or rolling the
NOSE UP/DN Wheel (GMC 305). Using this method, up to 200 feet
of altitude change can be commanded. To change the Altitude
Reference by more the 200 feet, use the CWS button (if equipped) as
described below, or climb/descend using another vertical mode (PIT,
VS) to capture the desired Selected Altitude.
• If the aircraft is equipped with a CWS Button, pressing the CWS Button
allows the aircraft to be hand-flown to a new Altitude Reference.
When the CWS Button is released at the desired altitude, the new
altitude is established as the Altitude Reference.
NOTE: While operating in Altitude Hold Mode, using the FMS Joystick to
change the Selected Altitude does NOT affect the autopilot (i.e., does not
change the Altitude Reference, and does not cancel the mode).
320
Altitude Hold
Mode Active
Altitude Hold Mode
Garmin G3X Pilot's Guide
Altitude
Reference
Altitude Hold Mode Softkey
Selected
Altitude
190-01115-00 Rev. K