Buyers and sellers dont have to post the entire order at once, for bigger orders most do not. In this case, a seller has a bunch stock to sell @2. He might be showing the intent to sell 2000 but he could really have 10k more 'behind it'.
This is common, it helps the buyer and seller get a better price and prevents a sudden or panic price fluctuation.
For example, if someone posted a buy order for 500k shares, the stock would jump up as traders would try and front run the order in an attempt for a quick scalp. If that same buyer posted that order a little bit at a time, they would get a much better price for their customer.