The other problem is that real estate footage isn't well correlated to the actual number of square feet in the room. The advertised number is anywhere from 20% to 50% higher than the actual depending on the location and realtor.
There was a couple of years ago a real estate agency in Paris that would advertise a minuscule 1 bedroom apartment, wrote it has 24m² floor surface, in the description said it "feels like" 16m² (it was legally 12m² with a ladder to an attic where you cannot stand upright).
It isn't technically, but very few people get prosecuted for it, so they do it anyway.
That was actually one of the fraud charges brought against trump in the NY lawsuit.
Relying on objectively false numbers to calculate property values. For example, Mr. Trump’s own triplex apartment in Trump Tower was valued as being 30,000 square feet when it was 10,996 square feet. As a result, in 2015 the apartment was valued at $327 million in total, or $29,738 per square foot. That price was absurd given the fact that at that point only one apartment in New York City had ever sold for even $100 million, at a price per square foot of less than $10,000. And that sale was in a newly built, ultra-tall tower. In 30 year-old Trump Tower,
the record sale as of 2015 was a mere $16.5 million at a price of less than $4,500 per square foot.