They are counting everything with an ISBN, including bound copies of the annual report from the Board of Fisheries.
My more-or-less former employer, a state government agency, published reports with ISBNs. But we never sold them. And as far as I know, no one ever reported how many were distributed in print or via website downloads.
It would be interesting to know what goes into the statistics and precisely what the sources are. But folks need to keep in mind that books are sold not only in trade bookstores (B&N and the like, as well as independents), but by way of:
--Book clubs (Literary Guild, Scientific American Book Club, and many more)
--Warehouse stores (Costco and so on)
--Grocery stores, convenience stores, and so on
--Direct sales by publishers, including
vast numbers to public and private schools and school districts, as well as sales to government agencies and organizations (training and reference books used by firefighting agencies, to cite one example I am familiar with)
--College bookstores (large market, perhaps not counted in general bookstore sales)
--Newsstands (in airports, for example)
--Book fairs (at schools, and perhaps sometimes at libraries and other public places -- the Books Are Fun temporary locations, for example)
--By speakers, lecturers, and teachers (for example, Learning Exchange and the like), "from the back of the room" (those numbers can add up, by the way)
--By visiting authors at school and library events (I know authors who specialize in those sorts of events and sales, getting paid not only a fee for the presentation but also for books sold at the event)
--Crafts and fabric stores (Joann's, for example)
--Hobby shops, and stamp and coin stores (not that there are many stamp stores left)
--Art-supply stores
--Coffee shops (Starbucks is the best known, but probably not the only one)
--Via magazine and newspaper ads (especially in publications targeted to special interests, such as guns, model airplanes, health and fitness)
--Via direct mail advertising (Rodale sells a lot of books that way)
--By authors via websites and other means (I have bought books by professional writers, published by large commercial publishers, at authors' speaking engagements, for example)
--By authors at regional events (one author-publisher of my acquaintance sells as many as
500 books per weekend at such events, and his total sales have run well into the tens of thousands, probably well over 100,000 by now)
--Via souvenir shops (every area of any size or interest has local-interest books offered in local-interest stores aimed at tourists)
--Via museum stores (the California History Museum, for example, has an attached store with books and memorabilia, as does the California Railroad Museum, both in Sacramento)
--By subscription (Library of America, anyone? I have about 110 volumes in that series myself; Time-Life used to sell tons of books by subscription, and might reenter that business some day; Harlequin sells paperbacks by subscription in at least a couple of categories, four books sent out about 17 times a year to subscribers; etc.)
I have probably omitted several venues. Heck, even liquor stores might carry a few paperbacks, and maybe a hardbound bar guide or two.
--Ken