I stand by the approximation. 300 m^2 is about 17.3m on a side, 17.3 m in feet is a touch under 57 ft. Rounded to one sig fig because I'm not carrying any sort of precision through these estimates.

Edit: Or are you talking about the "60 feet square" bit? I don't mean 60 square feet, I mean 60 feet on a side. I suppose I could have picked a clearer idiom.