The fact that it says 300% must be a capped limit because it should be closer to a 600% increase but there is a maximum the difficulty can increase we will find out in a couple of hours what exactly will happen but expect miners to jump back over to BTC and a day or so after the bitcoin difficulty will drop a bit making it even more profitable
Someone wrote earlier in this thread that it's capped at x4, so current difficulty plus 300% is the same thing.