So, looking at the scenarios in the rules, they use the following tiles:
1B, 1C
2B, 2C
3C
4B, 4C, 4D, 4E
5B, 5C, 5D, 5E, 5F
6B
7B
Which, for a start is only 16 tiles, but also, the numbers and letters imply that there are way more than 18.
So, future Tile Packs, d'u reckon?