Window
The report month. Releases and download change are both measured on it, download change against the previous month.
How it is computed
Plugins are placed in groups by popularity rank at the end of the prior month, then within each rank by release count in the report month, 0, 1 to 2, or 3 or more, then the median download change is taken within each group. The pairing is an association and not a cause: a release generates downloads of its own.