[snip]
Not sure if this is the best meme for the joke.
It's funny because you can't tell from a literal reading of the card's text whether this is what the card is supposed to do or not.
You'll have to use (gasp!) common sense!
Failing that, the rulebook makes it pretty clear.
The card text says "putting it on top of your deck", which implies you only ever gain a single card. It gives context that leads you to the correct interpretation.
"You may gain a Poor House for each card discarded, putting it on top of your deck". This still works. "You may buy a gallon of ice cream each Saturday afternoon, gorging yourself on it that evening."
EDIT: Granted, it's an awful, clunky, and unlikely sentence. But plausible enough to salvage the joke.