Near as I can tell, you always want to roll lower than the number for the skill. If you roll the number of the skill, trait or passion exactly (after modifiers), it's a critical success. If you roll a 20, it's a fumble (unless your modified skill, trait or passion is 20 or higher). Lower numbers are always better, unless you roll exactly of target number, then it's a crit. 20's are always fumbles, unless the modified target is 20 or higher, then you can't fumble.
There are also modifiers to the die roll itself. Lower numbers are better, so -5 to something is good, +5 is bad.
Let's look at Cedwyn's courtesy roll. He's got a 12 in the trait, which means he ordinarily needs 12 or less to be successful. I gave him a +2 penalty for still being dirty from the road (his appearance would have distracted people from his manners). His modified skill is thus 10. He rolled a 14, which is a failure. If he rolled a 10, it would have been a critical success, and probably earned him some Glory. If he rolled a 20, that's a fumble, and he probably would have made a scandalous social gaffe.
The above covers unopposed rolls. Opposed rolls are somewhat different - you have to roll under your target, but higher than your opponent. It's a little more nuanced than that, but that's the basic gist.
Make sense?