If my recollection is right it is a leftover from the time that your license had restrictions on those numbers. I may be wrong here (maybe somebody from Mendix can correct me here) but I think they are no longer in use by the license mechanisme. Allthough they are probably still used because when running locally you can not have more then 10 concurrent users in your local app.
Unfortunately I do not have formal documentation for you, but some testing on my end revealed that these statistics do NOT reset when an application is re-deployed or restarted. They would only reset when the environment is cleared down or restarted for the first time. As I understand it, these statistics are meant to be lifetime stats. For a more up-to-the-minute description of the number of concurrent users, you can use the ' User accounts and login sessions' chart on the Monitor tab as explained here: