This is super unreliable. I clicked through a few of the listings and none of them were what this site seemed to think they were. In one case it said a unit had 50 acres of land, and when I clicked through it was a two-bedroom condo with no land. Another said it had 1400 acres of land and when I clicked through it was 0.14.
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The issue is how the MLS (multiple listing service) allows listing of condos/apartments/etc. Since each unit has no actual land to itself, they're allowed to list the total land that the complex sits on for each unit. There's also basically no oversight or correction on what gets listed, so listing agents have no reason to be accurate or perspicacious.
Everyone then scrapes or subscribes to the MLS data. It's why you have a dozen identical realty sites: Zillow, Realtor, Redfin, Trulia, etc.