How did you come up with that number?
By my math, assuming that each fish has a 50% of being either gender, the odds of them all being one gender is less than one percent. Two would be 50% chance, three would be 25%, four would be 12.5%, etc.
Now that is assuming that they are all random genders, and sometimes weird things can happen in the environment or the fish selection process that give unbalanced ratios.