I'm probably going to out myself as a n00b here, but I'm having trouble understanding how someone could short a couple million shares of SPY, apparently outright. Check attached screenshot. Did they sweep the book? Is it real? Why does this happen?
i think those misprints of huge volume are transactions by institutions based on private negotiations, not traded on public venue. if you look at the source of those transaction, it comes from third party in esignal.