It looks like green mark does not appear at all (or with quite a long delay).

I tried following options:
1. completing a task "normally" (to the end, without exiting at any point) -> no green mark
2. Exit in the middle of task, selecting "Save&Exit" -> no green mark
3. Exit in the middle of task, selecting "Exit without saving" -> no green mark

I think at least in options 1 and 2, a green mark should have appeared at some point, preferably rather soon.