Cycle day 4 why is my OPK so dark???

mombie.89 momma of 4💕

Period just ended yesterday and I’m not taking any chances I started opks immediately! I am trying to understand why it’s so dark already 🤷🏽‍♀️🤷🏽‍♀️🤷🏽‍♀️ I know it negative but I didn’t expect it to be so dark so soon.