Calculation of number of active users

I ran two simulations, one for a little over 2 hours, and one for little over 8 hours. Both were equal with the same ramp up and load (constantUsersPerSec), and the results were also pretty much alike with the same responsetimes and throughput.

In the Gatling report the “Active Users along the simulation” showed about 60 active users for the shorter simulation, and 220 active users for the longer simulation. Why this difference in active users when the simulation length increases?