that means that someone has a sell order at .0042 for 3m shares or so. There are times that when a sell order is placed for a higher price, the MMs bump up the Ask tier by the same amount. I just tested it by placing a 5m sell order at .0042. The Ask spiked to over 8m shares, and came back down to 3m when I cancelled the order.
If that order is cancelled the 3m wall will disappear.
Register for free to join our community of investors and share your ideas. You will also get access to streaming quotes, interactive charts, trades, portfolio, live options flow and more tools.