The V2 UI allows users to optionally specify a test case when selecting a timeseries. When the user does not specify a test case, it fetches a special "summary" timeseries that uploaders produce for this purpose, so that the frontend does not need to fetch all of the data for all test cases and dynamically merge them. We recommend sheriffs configure alerts for per-test case (not summary) timeseries only, so there are not usually alerts associated with summary timeseries. This can make the UI confusing when the user sees a clear regression in a chart: there is no alert icon on the chart because the summary timeseries doesn't have an alert, but one or more test-case timeseries does. In order to prevent this confusion, the frontend can request the summary timeseries data at the ANNOTATIONS level of detail (including statistics, alerts, and sparse diagnostics), plus the timeseries data for all test cases at the ANNOTATIONS_ONLY level of detail (including alerts and diagnostics but not statistics).