The table isn't as complicated as it looks but some examples should help clarify.
Ulfons the Wizard
Let's start with Ulfons the wizard and his 5th level class features. At 5th level a mage gets a bonus meta-magic feat and the abiltiy to cast 3rd level spells. Therefore the class level of feature is 5. Since the training chart references levels from -2 to +2 with respect to the class level of feature we will look at levels 3 to 7. For reference, the experience for these levels is:
The table below shows the DC modifier for mastering each of these features at various amounts of XP for Ulfons.
|XP||Train-Ahead Modifier||Without Trainer Modifier|
For example, at 7200 XP, Ulfons is 1200 XP into level 4. This means he is 70% from level 5. Therefore the modifier is 7 since at 7200 XP, he is just one level below the class feature level. At 3900 XP, he is 70% from level 4. Now the DC is 10 + 7 or 17.
Specific Examples with Ulfron
Ulfons is nearly to level 5 and he happens to be at the tower of his mentor but the party is going on a trip and he thinks there is pretty good chance he will have the XP for level 5 well before he can get back to the tower.
Therefore, Ulfons tries to prepare for level 5 ahead of time. He engages with his mentor to study both his 3rd level spell casting and his new metamagic feat (he would need to identify the feat at the time naturally). He has to pay the mentor just as much as if he were studying at level five and spend the same amount of time.
He happens to have 8900 XP. This puts the XP modifier at 3.
The DC is 11: 5 + (class feature level/2 rounded up = 3) + (XP modifier = 3)
He does not roll at this point. He only rolls when he hits level 5.
At level 5, he rolls for the spells and the metamagic (since he trained ahead for both in this example; it is possible to train ahead for just one if you like to save time or money).
He rolls for spells first. Here he can add his intelligence modifier which is 3. He rolls a 3 which is not enough (roll: 3 + int modifier :+3 < DC 11). He tried to learn his 3rd level spells but just couldn't master it.
Now he rolls for his metamagic feat. Here there is no modifier, he just needs to roll an 11. He rolls a 10. Poor Ulfons, he tried to train ahead but failed.
Without a Trainer
Somewhat annoyed at the wasted money and time, Ulfons returns to the wizard's tower only to find it has been burned to the ground. He has no trainer! He decides to master it on his own.
Ulfons has 13700 XP now. The XP modifier 13. So the DC is now 21 but he does get the +3 intelligence modifier for his spell feature. The party is staying in town for a few weeks while other more fortunate party members visit their trainer so Ulfons decides to try to learn his spell feature. He only needs to pay for materials now since there is no trainer to tip/pay. Of course, there is also no trainer to give him 3rd level spells but Ulfons did find one 3rd level spell on his adventure.
Ulfons rolls a 19, with his intelligence modifier he makes it! Had he tried for the metamagic feat, that would not have been sufficient and he would have failed.
Later at level 6 with 17400 XP, he tries for his metamagic feat. Earlier he had tried for still spell but since he failed, there is no reason he can't change and try for silent spell this time. At 17400 XP, the modifier is 6 so the DC is 5 + 3 + 6 = 14.
Ulfons rolls a 8 and fails. Poor Ulfons but at least his misfortunes help illustrate the system for us.
Time passes. Ulfons attains the lofty level of 7! Now he has 23150 XP. The DC is 5 + 3 + (-3) or 5. Ulfons rolls a 19 and easily makes he. Finally, at level 7, he has both class features of his 5th level class. Of course, at level 7, now Ulfons is trying to master 4th level spell casting. He considers changing his name from Ulfons the Brilliant to Ulfons the Unfortunate.