Complex sentence: The reason for this is to make breeding more of them a little harder, one in eight of them are female though (this same gender ratio exists for other non-legendary Pokémon that you usually only receive one of).
Split into simpler sentences: The reason for this is to make breeding more of them a little harder. One in eight of them is female though (this same gender ratio exists for other non-legendary Pokémon that a player usually receives only one of).