Calculation of probability

Exploration Stage: Red Rose Cafe
From: Adeline Svensson
Description: This investigation is taking an unexpected turn! The winner of the tournament bet on odd items that for some reason Master F needed. What was so special about these items? Let's find out quickly! Let's look for the abacus that left the hands of the fourth winner.
Completed: Only the abacus can calculate probabilities. I once wrote an article about this, but it was a very boring topic. Look. There is a piece of paper attached to the back of the abacus!