Garmin G3X Pilot's Manual page 232

Hazard Avoidance
A Proximity Advisory (PA), displayed as a solid white diamond or triangle, indicates
the intruding aircraft is within ±1200 feet and is within a 6 nm range, but is still not
considered a TA threat.
A Non-threat Advisory, shown as an open white diamond or triangle, is displayed for
traffic beyond 6 nm that is neither a TA or PA.
Relative altitude, when available, is displayed above or below the corresponding
intruder symbol in hundreds of feet. When this altitude is above own aircraft, it is
preceded by a '+' symbol; a minus sign '-' indicates traffic is below own aircraft.
A vertical trend arrow to the right of the intruder symbol indicates climbing or
descending traffic with an upward or downward-pointing arrow respectively.
Flight IDs may also be displayed with traffic symbols; see the Flight IDs discussion in
this section for more information.
214
Intruder Altitude and Vertical Trend Arrow
Garmin G3X Pilot's Guide
Relative Altitude
Vertical trend arrow
190-01115-00 Rev. G