@OptimusPrime It’s likely that this news article is using a different data source (e.g. instances.social) but you can go to [software].fediverse.observer/stats to see the data that @fediverseobserver has collected about this (their numbers are usually lower than the popular data from instances.social due to excluding dead instances, but they include Diaspora). For example, lemmy.fediverse.observer/stats shows 1422 monthly active users for Lemmy.

https://the-federation.info/

Click ‘active last month’, either for the whole Fediverse or after selecting a platform from the list.

The Fediverse Observer has a stats page.