As you probably know if you learned the rules, there are 3 kinds of mythos cards (green, yellow and blue) and three difficulty levels (easy, medium, hard).

The face up mythos cards are used by the script to make a random mythos deck. You can also use them to create a custom deck if you prefer to do it manually (some people don't trust the AI's randomness).

AHh ok. It's as I expected. The face up ones are just duplicates of the face down ones if you want to manually set it up using specific difficulty level mythos cards.