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The dashboard is reachable from the top menu, when clicking on the Sprints Dashboard tab.
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In the page opened, you can view the following:
Backlog %
Total tasks
Overdue tasks
Completed items in %
Story points spent per sprint
Average story points spent per sprint
Planned vs Actual percentage over sprints
Potential vs Planned percentage over sprints
The calculations are affected by the Jira board settings (Board settings → Estimation → Estimation Statistic). The available options supported are: Story Points or Original Time Estimate.
In addition, you can create reports for individual teams, sprints, and version. The default is showing the data for the entire project.
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