Plugin’s total number of users

I do not think that this is possible.

This numbers are only calculated by which Version has been downloaded (+1 to the absolute Download statistics) and if an Update changed the Version (-1 to the former and +1 to the current, used for the percentage).

I am not really sure about the second part, but it has to be something like this. Maybe a bit more sophisticated 😉

Unfortunately, there is no way to tell exactly how many Websites run your Plugin, let alone the Version of your Plugin. There are far too many factors of fuzziness (closed systems, unofficial forks, …) to know the number. You can only make an approximation using the given stats.