It's on page 31.<br/><br/>"When using an exhaustion talent for major gain, the character increases the degree of success by the number of exhaustion dice he has, in addition to rolling those dice.  Magor uses of the talent require that the player voluntarily increase his character's exhaustion by one as part of the roll."<br/><br/>Basically, a major use is "I want to use my Exhaustion talent to get this sort of bonus on this roll".  It isn't explained too well, alas.  Took me a while to get it, too.