The rules

Each winning tile pattern is written in a little code on the card. Digits are tile numbers, F is any flower, D is a dragon, and N, E, W, and S are the four winds. A 0 (zero) is the white dragon playing the number zero (remember the soap?).

Repeated characters form a group: 999 is a pung of 9s, and 9999 is a kong (see? Those chapter 2 words are already paying off).