Subtract the number of baptized jws from the circulation number and you get about 16,000,000 magazines that are read by non-jws who likely have little intention of ever converting.
Then subtract from 16 million the number of copies sitting in closets and on bookshelves of the averge dub for many months before they are tossed out (or left in laundromats to be tossed out by others). If the average dub has 2 or 3 copies of each issue lying around, and you multiply that by 6 million, that doesn't leave much "circulation," does it?