The doc was found during discovery by Apple's lawyers as part of the latest round of patent infringement lawsuits between the two electronics giants. According to the chart posted by Forbes, Samsung believes they sold around one million tablets in the US in 2011.
This was during the period that Samsung was caught out with the lie that they had sold 2 million tablets in the first quarter of 2011, but later had to walk that claim back and admit that they had made 2 million tablets but had not actually sold them all.
Now we know that Samsung had sold only about half that many. That's a million tablets for the entire calendar year, not just a single quarter. In comparison, Samsung believes that B&N sold 1.5 million NookColors in 2011.
This same chart says Amazon sold 5 million Kindle Fire tablets after it was released late in the year, but even though both Samsung and B&N were outdone by Amazon that doesn't change the fact that Samsung was still thrashed by a bookseller which at that point had only released a a couple ebook readers and a couple tablets (counting the Nook Touch in mid-2011 and the Nook Tablet in late 2011).
Those were Barnes & Noble's glory days; it's a shame they didn't last.