Board Thread:Breeding Questions/@comment-13710950-20130804143717/@comment-10760902-20130806010335

Hello CoolM.E :P. As far as I know, YanKizon has already answer this question.

I hope you've read this page, I've written this very clearly: Rate Value. Here is a brief summary of that page: Therefore, depends on which dificulty of your "target" dragon, the final chance will be decrease or increase when you grow up your parent dragons.
 * Don't call it that way, it might get you confused. The best name should be Total Rate or Rate Value. Which is calculated by sum of two parents' revenues (gold/income) => will change on leveling up.
 * This value defines which slots are open of each dificulty. Every dragon is signed to a dificulty group, there are total 3 dificulty groups.
 * With different slots opened of each dificulty, chance of each dificulty will vary. So basicly, Rate Value (Total Rate) => affects Slots Opening => affects % of each dificulty group => affect % of all the dragons in that dificulty group.

P/S: it took me ~1 week to understand the breeding system. But once you know, you will know xD