If I remember right (haven't played for too long) FFVIII's system makes you need 1000 exp. per level, so if you're a lot of levels above them they'll give less exp instead of you needing more- so it seems like an ever changing number. I'd assume it's some statistic that translates into something else. Having 100 str does not mean you'll deal 100 damage, this would probably be something like that. The more exp it say in the guide the more you'll gain but you won't gain the # it says.