What is important about this number is not its total size, but its change per day. The device count and membership only points to the number of registrations.

Yesterday, 65,983 device reported at least 1 WU. The extrapolated total of about 100,000. If you include the random probibilty based on the average system that turns less than a result per day and the same factor for the units that came in that didnt turn a result the day before, it shows ~40% dont.

There can be more, but they would have to turn a WU every 4-7 days.

Both members and devices are only counted if a result has been returned, so it can really be said that atm 311 thousand 'members' and 685 thousand devices send in a finished work unit. Latter a little more debatable as a re-installation generates a new device, but on the other hand a quad or dual / tripple duo or a mac mini computer does also generate only one single device.