As so many have said (and as is found in one the little Owner's Manual booklets they give you), Nokia often goes through several different code names throughout phases of the development process. Seeing as this is the successor to the Preview 808, they likely started out with the name Lumia 909 before it received its final, launch title, the Lumia 1020. It has no impact on the device, it's just a fragment from the different phases of development. A little weird, I no, but nothing to worry or fret about.