Your data is for North America; the report was worldwide. Android tablets have a MUCH greater penetration in Asia, especially. Just like Nokia is the biggest cell phone maker in the world, but barely registers anything in the US.
Please do not try to stretch US results to cover the entire world.
That's funny, Apple just surpassed Nokia as the world's top smartphone vendor. You heard it right, WORLD. Nokia has high volume because of all of the cheap, low-profit standard phones.