Hmm. What brand / website? Or how much did you pay? We can better estimate what you really have
If that is true wattage, for a 3x3? Damn! Even if it's not true wattage I would assume there's enough power to flower with. I'm by no means knowlegable about leds tho. About to get some cobs myself in a couple months
Edit: your 300 watter is 70 watts. Just read that.