Backlogs require continual refinement to prepare the stories for development.
This visual focuses the team on the stories that are either not yet estimated or those that are too big to be taken into development and need to be broken down further.
This shows all the requirements (user stories), the relative sizes are shown on the X axis (2).
The numbers of items of that size are shown in the columns (1). Teams will be interested across a few of the states, which are chosen at the top (3).
Teams may be particularly interested in the larger stories that need to be split down into smaller requirements, or they may focus on the unestimated backlog items.
Like all SenseAdapt charts it's possible to click on the chart (1), see details of the items (2) that require refinement and then open them up directly in TFS