Well, that's only a third-party seller's item description, which is probably a guess based on Zavvi's "Ultra limited" moniker.
If you look back at the posts in this thread, there are a few discussing the term "Ultra limited" typically meaning 2000 or 2500 units with Zavvi's past steelbook releases, but nobody mentions that "Zavvi's product page says 2000 copies" or something similar.
There are several steelbook products at Zavvi's store with the term "Ultra Limited", but for which the actual number of copies hasn't been specified, e.g., Moon, Kill List, They Live, The Others, Training Day.
Edit: I find it surprising that Zavvi doesn't specify the actual number of copies for all of their "Ultra Limited" releases. Not that I place too much trust in Zavvi, but I just can't quite believe that the print run would be much more than 2000 copies for a catalog release like this, when even many Disney steelbook releases struggle to sell 4000 copies.