I noticed some similar queetionable stats a week or so ago. Maybe they don’t get rebuilt right after an upgrade? Or sometimes it fails for some reason and old stats stay around?
I know newly joined members don’t make it into the User page for a while. AFAIK a once-daily sidekiq job.
The Admin → Users → Active and Admin → Reports → Visits look reliable. I am certain only 4 “members” logged in to my localhost dev site during the past week (in an attempt to repro multiple Notifications).