The sprint burn down chart shows the remaining effort in the sprint. The blue line represents the ideal trend. The red bars represents the actual effort. Days that are non working days won't be displayed in the diagram.
If you don't track the working times as descriped in Section 1, “Time recording� a done task will have no remaining effort on the last day of the sprint.
The Figure 21, “Sprint burndown chart� shows that the non working days won't be displayed (1st to 3rd March).