it doesn't have a certain level of occurring, it is even not certain and definite itself; and @jcornel explained it great, it doesn't mean if it happens several time through time, there would be same falls.
BUT
the better question you could make would be: at what level if I hold BTC should stop loss and how low it may get?
I would say (and I'm just one person with some experience in trading) 6900$ is a critical level and 6000$ would be the next resistance (rough numbers)