The table in the overview simply shows what is entered/stored as laps for this activity. By default, this is what the file reports, but you can enter anything when editing the activity. The total distance and duration of these laps does not necessarily have to be the same as the total distance and duration of the activity.
However, the detailed view for your laps calculates all those numbers based on the exact data series. For this, it's necessary that total distance/duration of laps and activity match. In your case, the total duration of the laps saved for the activity is only 3:21:49 and one second is missing. That's why there's another lap shown. To prevent this, you need to edit the activity and add this one second to one of your laps.