It might be the pot odds
he's talking about.
If he got 40% chance of winning the pot, then he should call with almost anything. In this case I don't think that his chance is 40% though, but he'll be getting paid very good if he wins, and that is, sometimes, enough for some people to call with any two cards.
I can't remember the exact calculation for it, but I think that if there's 300 in the pot and the other player puts in 200, then you can call any draw, almost even a gutshot or a backdoor. At least if you've passed the bubble.
300+200 = 500 which gives you a good pay if you win. You have to put in 200 to win 500, which gives you the "right" odds to call many hands.
I hope it makes sense.