When importing activities into superset it appears that superset shows the duration of the activity to be from the start of the activity to the end and ignores any breaks.
While this works for activities like the gym, swimming or manually recorded activities where rest is part of the activity it does not work for walking, running or cycling.
This is because when doing something like a bike ride, if you do 1 hour cycling , then have a cafe stop for 1 hour then do another 1 hour cycle in the same activity it shows the duration to be 3 hours. Which is correct as duration, but really you want to know active duration, which would show 2 hours. More common examples of this would be even just running and having small but little chats as a break. But over a whole activity this can make 1 hour 30 duration only 1 hour active.