Garmin GTN 650Xi Series Pilot's Manual page 205

USER WAYPOINT IDENTIFIER
Assign a unique identifier or keep the unit generated identifier. If an identifier is
already in use, the three digit number increments automatically upon opening the
page.
User Waypoint
By default, the identifier format is
"USR" followed by a sequential
three digit number.
User waypoints are helpful when ATC requests that you fly one radial to intercept
another. While the point is often defined by an intersection in the navigation
database, this is not always the case. The Create User Waypoint function allows
you to define the new intersection and insert it into the flight plan in advance, as
opposed to using the NAV radio to tune each VOR and specify the radials to fly
inbound and outbound.
190-02327-03 Rev. C
User Airport
Identifier format is "A" followed by
a sequential three digit number.
Pilot's Guide
Navigation
3-63