From the Banishing Warden paladin archetype:
Banishing Smite (Su): At 3rd level, once per day when the banishing warden confirms a critical hit against a target of her smite evil effect, she can attempt to forcibly banish the target to its home plane. The creature struck must succeed at a Will save (DC = 10 + half the banishing warden’s level + the banishing warden’s Charisma modifier) or be sent back to its home plane as per dismissal. At 10th level, a creature dismissed in this manner takes an amount of damage equal to 2 points per paladin level at the start of its next turn. The banishing warden gains an additional daily use of this ability at 9th and 15th level.
This ability replaces the mercy gained at 3rd level. A banishing warden still receives the benefits of the mercy class ability starting at 6th level and onward.
To me the bolded sentence reads that the creature takes the extra damage only if the dismissal succeeds, and takes it only after returning to its home plane. Am I misreading? Or is there a point to this that I'm not seeing?