Even if these numbers were profit and not just revenue, it is is very possible for the shares to drop 15 percent. It happens all the time, although usually not at the 15% level.

The reason can be summed up in one word - expectations. If everyone was expecting a profit of around 1.5 billion (shares would have been trading accordingly) and results come in at 1 billion then clearly there is likely to a significant and immediate drop in the share price.