4DS - Anything but Charting, page-2954

I'm sure someone can provide a more technical answer, but I imagine that the stock rallied because of the initial excitement of the milestone being achieved, but as the morning wore on and reading the announcement in more detail and processing it, perhaps people thought they'd take a neat profit and jump back in a) once the details of the extension have been finalised or b) once 4DS approaches the next milestone. At the end of the day, there's still a chance that nothing will come of 4DS - so we can't knock people for recognising an opportunity to make some good cash in a couple of hours.