It is not significant because it only discusses the monster's rank and other minor details. If you choose to skip it, you may.
Here, the beasts are animal-oriented species, whereas the monsters are related species like goblins, orcs, and ogres.
Demons and highly clever spies like vampires, liches, dragons, and other creatures of a same nature are not present, despite my desire to include them to a magical being or something. But let's keep them on monster rank for the time being.
They are ranked in order from E to S.
Were E being the lowest and S being the highest.
And the rank for adventures goes from F to S.