Tutorial Step 7: Set Task Durations
Use the view switcher to get back to task view. Each task takes a certain amount of time to complete. You can set a task's duration by typing in the Duration column of the task outline, or by clicking and dragging the ridges on the right end of a bar in the Gantt chart. If you're typing durations, you can use unit abbreviations like 2d (2 days), 1w (1 week), and so on.
The length of the bar in the Gantt chart represents the duration.