25% of the payout is being distributed among the curators (voters) and the burned part (when voting before the 15th minute) goes to @null (back to the reward pool)

Going to the reward pool and going to @null is not the same thing.

Going to @null removes the rewards from circulation, and shrinks the overall size of the reward pool, by returning to the reward pool the rewards are redistributed and increases the potential rewards to all other authors and curators with pending payouts.