Thank you for this! It seems like there were 4 million new users in the last month but 250k fewer monthly active users. Maybe there is just a lag and the MUA will pick up in the next months.
Interesting charts, though. This will get a bookmark from me.
DAUs is indeed a much more meaningful statistic over total number of 'created' accounts over the past 7 years. That doesn't mean 13M accounts are using Mastodon. It is far less than that.
But I doubt that you will get a verifiable and up-to-date and official figure on the DAUs of Mastodon, as they do not show or have such a figure. So we can only make guesses at this point.