A character has a number of Unlucky Numbers equal to five minus their Luck Bonus. These numbers determine when they critically fail, and are determined at character creation. If a character’s Luck bonus drops by one or more, then change one or more of their existing Lucky numbers (player’s choice as to which ones) into Unlucky numbers so that their total number of Lucky/Unlucky numbers remains the same. See 1.1.5.1 Critical Success & Critical Failure for details.