When going through your own plugin details and checking the active version downloads. It's helpful to see which version that webmasters prefer, but I see no details on the subject on WordPress (and on here, yet). I recently had an unexpected change in stats, and I can't find anything as to what the time frame is. What few that I have found are either closed with little or no response, and/or indirectly related.
The active version pie chart can be found on any plugin under Stats.
Most of the time, new versions don't even show up until about a day or so, but is the timeline based on days, weeks, or months?
This says that it is based on the current active users. Which is interesting. Daily Tip: New Usage Graphs on WordPress.org Plugin Repository
Any additional information on how the chart actually works is helpful.