Window
A single date, the last day of the report month, and the number of days since the WordPress release it concerns. An issue may also show the number of plugins newly declaring the version each week of the report month.
How it is computed
Plugins naming the version in the "tested up to" field, divided by the plugins in the population. The field is declared by the plugin author and not verified, so the measure records what an author states, not a test result.