Wondering how its inaccurate, then? Im no expert when it comes to it, but i have never had a bullseye except from Darling, the only one who has ever mated with a rooster, and laid eggs in the flock.
I have had my other chickens for longer then a year, but when Darling got mated, she suddenly...
You cannot have eggs fertilized without a rooster. Unless you got the eggs from a place that had a rooster and hen mate to lay the eggs.
All look fertile.