When you “Start working” on a project the timer at the top of the screen starts at 5 minutes so that you can visibly see the time entry on the week view screen.
When you press the red stop sign next to the timer it will record the correct time.

For example once you reach the 6th minute the timer will increment as usual.

If you stop the counter at 3 minutes your time sheet will show a 3 minute entry not the 5 minutes.