Garmin GTN 650Xi Series Pilot's Manual page 224

Navigation
Altitude Constraint
Data Priority
GTN prioritizes altitude constraint
data for each navigation point and
displays it in the ALT column of the
active flight plan.
1. GTN honored constraints
(includes invalid constraints)
2. Reference-only estimated
crossing altitudes
3. Published reference altitudes
4. Empty (no altitude data)
3-82
ALTITUDE TYPES
Database Constraint
Altitude is retrieved from the navigation database and
designated for use in determining vertical guidance.
Pilot-specified Constraint
Pencil icon indicates manual designation or manual data
entry.
Invalid Altitude Constraint
GTN cannot use the altitude to determine vertical guidance.
Estimated Crossing Altitude
For reference only.
System calculated estimate of aircraft altitude as it passes
over the navigation point. Absence of bar(s) indicates it is
not a potential constraint.
Published Reference Altitude
For reference only.
Altitude is retrieved from the navigation database, but not
for use in determining vertical guidance. Bar above and/or
below the value indicates constraint type.
Pilot's Guide 190-02327-03 Rev. C