"A 10% chance is pretty unlikely, but everybody knows that a one-in-a-million chance is a sure thing!"
Wouldn't you say Durkon's odds of convincing Redcloak to go along with this are one in a million?
Well, yes, but there's always the risk they're one in nine hundred ninety-nine thousand nine hundred ninety-nine. You need the sweet spot. Narrative don't settle for rounding-up.