Q: So, are these distinct users per day, average number of users connected
over the day, or what?
A: Average number of concurrent users, estimated from data collected over
a day. We can't say how many distinct users there are.
However, I vaguely recall arguments that the number of simultaneously connected Tor clients, at any given instant, is rather smaller than this estimate, which is calculated as 10% of daily directory requests.
Is there any reason to think that's so?
Also, is it possible to estimate how many circuits are simultaneously in use?