I extended the volume so you can see it more easily. Intervals are 30-minutes. Yellow volume bars indicate price didn't change for that interval but doesn't mean price didn't change within that interval. I expanded the volume so you could estimate the volume values of each interval. The very large red bar represents the first 30-min interval of trade after the market opened (and 8.5 million of that took place at 6:30 during the first minute); and as you can see from the opening 30-min price bar, all of the pre-market traders got a good spanking, and their collective butts will probably glow red for a while. A good example of why you shouldn't mess around with trading outside normal hours.