It's usually two candles at least.
You can see it earlier on the very chart you used. There are two red candles, then a green. In the case of the chart you posted, it's a bit more in the earlier example. So, maybe it goes down a bit more, then back up, and down again.
If it is a 30%+ correction, yes. However, it isn't clear that's what it is at this point. Though history points to it likely being one of those.
I don't really consider the minor pullbacks on the way up to be "corrections". They're just adjusting to the outer bounds of the moving averages. It could most certainly enter a correction at this point though.
The lower correction actually looks like a flagging pattern. Usually the second flag only goes up a little ways, before going down a bit, so we should hope it manages to keep going up from here and not out a ways sideways.
Remember: Every time it does this there are a lot of people saying that it will keep going up and hit $100k or $1m or whatever.