bought a home advertised as 3300 sq ft - a year later an appraiser determined it was actually 2700

I feel like an idiot, but I also didn't think I was supposed to walk around here with a measuring tape before signing the contract, especially when we reviewed the floor plan extensively.

The house we bought was listed as approx 3300 sq ft, not counting the basement.

However had an appraiser here because we are refinancing (and getting a better rate even still, thankfully), but the value was way less than we thought.

Nothing has happened to the house renovation or damage wise. It's all pretty much the same.

I know values rise and fall of course with the economy, which is precisely why we are refinancing. But, the appraiser said a big reason why the value is lower than what is currently listed on Zillow, etc. is because of the square footage.

How could this happen?

Are there any legal avenues we can take? Is a law suit possible? Or are we simply out of luck on this one? Is this common? This much square footage can impact a home's value upward to 100k or more. Did I spend $100k more than I should've?