Garmin GPS 400 Pilot's Manual And Reference page 217

Message
Waypoint memory is
full
190-00140-60 Rev. E
All 1000 user waypoint locations in the GPS 400's memory have been used. Delete
unwanted waypoints to make room for new entries.
GPS 400 Pilot's Guide and Reference
SECTION 12 – MESSAGES,
ABBREVIATIONS, & NAV TERMS
Description
12-7