But it doesn't? If the bait dose is 80mg, then 500 doses would be 40,000mg. I think they must mean 500mg -- that's consistent with the toxic dose being 200mg/kg in dogs and 10mg/kg in cats [1]. The phrasing is super bad, I wonder if it was altered by a copy-editor who added a unit but misunderstood the intended meaning.
[1] http://www.ebvet.com/forum/viewtopic.php?f=9&t=383