Well, the gross square footage usually is counted from the outside, right? Then you add walls on the inside so everything shrinks.

What would really bug me is if the final layout was nowhere close to the representation, and the gross footage was not what was offered. However, I'd also be erally bugged if they gave me a triangular house that met the above requirements--I've seen things like this where they squeeze things into curved lots and create askewed houses that make the flow through the house impractical.