You should have a date column linked with the calendar table in order to create a burn down chart. The above information is not enough. Please refer to the video and post below. You can add the tree type in the legend in your case.
All visuals including charts are based on data table not on others visuals. Can you share the sample data table not a visual table, A sample pbix would be best. Also include the relationships, because it seems the date and incomplete item column are not in the same table with your fact table.