I can't guarantee you'll like the answer any better, but the reason this exchange happened the way it did is not because lawyers are incapable of understanding simple concepts. It's because the guy being deposed and his lawyer are doing their very best to be absolute pains in the asses to the lawyer asking the questions (to the extent that they can without a judge reprimanding them).
Backing up a little bit, why is this guy being deposed? A literal answer might be to say he's being deposed so that the lawyer asking questions can find out about his office setup. The better answer would be that he's being deposed because someone sued his office to try to force them to do something they don't want to do. The more forthright this guy is, the worse things turn out for the office he works for. So he's resisting tooth and nail. It ain't pretty, but it ain't hard to see why he does it, either.