The listing page's source code shows the remaining count. The number decreases as people make orders and the item sells out when it reaches 0. Many here have assumed that each time they do a batch, they are actually selling that many units. I have no doubt that there are enough orders to add up to the total number offered, but I do doubt that a significant portion actually pay. I don't believe Bitmain is selling from a pre-defined number that they already have planned to make. Rather, I think they have a general idea of how many they want to sell and continue to put out batches of "20,000" until enough people actually pay and they reach the number they're shooting for. We may have seen 100,000 orders go through, but I'd wager that less than 30,000 will actually be paid for and shipped. That's still a huge number and I'm totally speculating here - I have no insider knowledge and could be completely wrong. We won't know for sure until November.