The asterisk means that, by “active users”, they’re considering only those who commented and/or posted “in the last month”. Maybe join-lemmy’s algorithm is considering from “day 1” of the current month, so a time span of 10 days, against 29 days from the second screenshot?
If it’s true, it kinda of statistically makes sense: 10 days (28.4K) versus 29 days (47.8K), 34.4% of days with 59.41% of users. We’d need to wait till the 29th day to really compare the difference.
Also, “only those who commented and/or posted”. Sometimes, people can become much of an observer, just seeing and voting up/down, without actually commenting or posting.