The codes are four-letter words, and the clues between each letters shows how far apart the letters are alphabetically. The tutorial uses "REEL" as an example, in which "R" is 13 letters above "E" (hence R 13> E) and "E" is 7 letters less than "L" (so, E <7 L). Some people do a little trial and error, some start with the first letter and count up and down the alphabet, the tactic I prefer is finding what would be the "lowest" letter in the code word and working around that, starting with the letter A in that place and counting up and down using the clues until the correct word forms. I hope that helps, thank you for checking out my game!