The pie-chart gives a bird’s eye view on the distribution of cards tagged to an ART. The pie-chart visually shows the distribution of cards based on three key work stages – Backlog, Work-in-progress, and Completed cards.
Each of these stages is represented in a unique color and hovering over any division shows the stage name and the percentage against the total number of cards.
You can expand the view to a bigger size by clicking the Expand 
icon.