These charts are available as summaries for all the tests you have run, or as a summary of each project you've defined in TestProject. You also have the ability to filter the data that you want to show up on each chart. There are some useful built in options for quick filtering like
Last 30 days or
Last 20 Executions or if you want you can create a custom date range for the chart. In order to change the range of the chart, go to the select range dropdown on the left of the page and choose the option you want.