If I run for 20 mins and press "Lap" in the middle, I get one 10 min lap. I think it would be more logical if I got in the situation above two laps, one from the start to the lap signal and another from the signal to the end.
Another possibility would be to leave out the time between the start to the first lap signal and also the time from the last signal to the end. In this case the laps would only be those between two lap signals. Thsi is the logic my heart rate monitor (old Polar) works: Firt there is a warm-up period, then one or more laps and finally a cool-down period.
Personaly I would prefer the alternative with the start and end periods as laps.
PS I am using SportsTracker with E66 which is not officially supported, but I don't think this feature depends on the phone model.