It can't be bad. A stock can jump after hours on rumor or news and that would be great for us, but a lot happens after hours and the fluctuations can be wild with less volume/higher volatility (although a 300% jump is significant)and can still fall back to closing price the next trading day.
It'll be interesting to see what this is all about, but I wouldn't expect it to be more than AH manipulation or rookie mishap. But, anything is possible and it can't be bad.