In this chart I added a new set of rows so that we have 3 groups of data to try to capture all work including bugs and "new" stories (i.e. stories that were not in the original sizing but added after that point).
- Blue line is expected stories remaining as usual
- Orange line shows actual stories remaining as usual
- The Red line shows bugs and new stories that were added
- The green line is formed by assigning zero points to all "new" stories on day 1 and then adding a "bump" column in between day 1 and 2 and then burning down all stories (those originally included AND bugs AND new stories)
I prefer blue and green lines alone: The slope of green and blue should be roughly the same and the gap between them shows how many things were added to the sprint.
If you show blue, orange and red then you can see similar information, but it's harder to compare the slope of blue (projected throughput) with the combined slope of the red and orange.