All the examples below are for a 20 level character. I may be incredible thick not grasping the spirit of the law, or there may be others that could misinterpret the rules, run into a zelous DM and handed a jolly good XP-loss spanking.

RULE WORDING
– 3 Levels of Each Class at Level 20 (3b20) Rule: A PC (the build plan) must have 3 levels in every class at level 20 (example of a build's class level distribution at the 20th character level: 17/3 or 14/3/3/ or 11/3/3/3). Prestige classes are included in this rule. So for example, a Rogue 12/Wizard 5/Arcane Trickster 3 is okay. A Rogue 13/Wizard 5/ Arcane Trickster 2 is not. Failure to observe this rule will result in the de-leveling of your PC to a legal state with NO XP refund!: A PC (the build plan) must have 3 levels in every class at level 20 (example of a build's class level distribution at the 20th character level: 17/3 or 14/3/3/ or 11/3/3/3). Prestige classes are included in this rule. So for example, a Rogue 12/Wizard 5/Arcane Trickster 3 is okay. A Rogue 13/Wizard 5/ Arcane Trickster 2 is not. Failure to observe this rule will result in the de-leveling of your PC to a legal state with NO XP refund!