There are 4 symbols in order to create a cheat code. Number 1 represents the first symbol. Number 2 represents the second symbol. Number 3 represents the third symbol. Number 4 represents the fourth symbol.
However you need to know what the first symbol is. :P The first symbol is the "e" turned to right.
Unlocks a set of cards: 2111 - 2112 - 2113 - 2114
If you have any questions, feel free to ask them here. ;)