The Reports page helps visualize activity across Stories, Epics, Milestones, and Projects. Reports can be viewed either within your current Iteration or a custom timeframe.
Stories that are included on the Reports page are ones that have been moved into a "Done" workflow state. You can review your Workflow States by clicking on Settings (gear wheel) > Workflow. More on how to define your Organization's Workflow here.
If a Story is moved to a "Done" workflow state and subsequently moved back, it will not show up on the Reports page. Once it is moved back into a "Done" state, it will only show up in the Report for the final/updated date range.
Setting Your Custom Timeframe:
The Timeframe defaults to the date range of your current Iteration, but can be adjusted to show activity between any two dates of your choosing by clicking on the "Activity Between" drop down menu and selecting your desired start and end dates. Please note that dates on your Reports page reflect your organization's UTC offset, which can be configured via Settings (gear wheel) > Organization Settings.
View Reports within a Custom Timeframe:
If your Organization uses Iterations, their length and start dates can be set in Reports Settings (more on that here). You can review your progress as a whole or filter across Projects, Epics, Milestones, and/or Labels, all on one page.
Jumping To Your Current Iteration:
Navigate to Next or Previous Iterations: