What am I missing about sq footage coverage?

I feel unbelievably dumb. While reviewing coverage of different units and brands (currently leaning towards a Wilson) the reported sq foot coverage seems very out of line with the “room coverage”

Unit descriptions will often say something like 3000 sq feet, good for 1-2 bedrooms. This doesn’t seem to be restricted to one brand or article.

I’m trying to find a unit that I can—hopefully—put on the corner of my house closest to the metal barn (approx 100 feet away) to get just the tiniest bit of coverage in there as well.