To create a timeline in Qlikview, you need to use the duration of a task as the expression and the startin time as the offset. You are using the average of duration as the expression and duration as the offset. Besides this, your data covers more than one day.
If your tasks start everyday on the same time, and you want to draw the avg of duration, you can use this avg duration as the expression and the starting time as the offset.
Please, send more details of what you're trying to achieve.