I followed this link and using the Server Wizard found that my biggest local instance is run by an experienced FOSS and business guru in my hometown. Thanks. I have to meet this guy now.
Are they including Gab users in the MAU count?
No, since Gab does not federate with mainline Mastodon instances anymore.* I'm not sure if Gab discloses its stats the same way other instances do.
For some things, Wikipedia is a really bad source. Especially about things they hate.
Well, the source is The Interecpt, based on leaked internal data, which I trust a lot more than stat aggregators like Alexa. If you're the CTO then you could just answer the question: how many accounts (or unique IPs, if multiple accounts is common) have posted something in the past month?