I have an Edge 500 and have Garmin Express installed. Connect always shows a (1) update available in the Device Sync tab and says it's:
Time Zone Map, Version 16.02
When I click Send Now, it opens Garmin Express and does a sync. Garmin Express shows that everything is up to date, with no Optional Updates. The problem is the notification in Garmin Connect doesn't clear. I can click the little "x" to remove it, but eventually it'll come back again.