Folder History -> Chart

 
At the top of the Chart section is a toolbar that is used to customise the chart's content.
From left to right;
display in terms of the number of files belonging to each category.
display in terms of the size of files belonging to each category.
The centre fifteen buttons toggle the relevant categories from the chart display.
The magnitude buttons have the same effect as the equivalent Files buttons, in that they show the size and quantity of files displayed according to the magnitude of the file's size.
The left hand side of the Chart tab shows a list available scan dates. Clicking an entry will show the number of files, folders and total size for that scan in the area below the toolbar. Selecting the entry (tick the check box on the left) will add that scan's data to the chart.