As everyone said above, if the animals are as advertised, 100% het for clown, then each egg has a 25% percent chance of being a clown. The reason you see so many chances at 66% het for clown is this. Each animal can throw one of two genes. They will either throw a clown gene or a normal gene. If the male throws a clown gene and the female throws a normal gene, the resulting offspring will look like a normal but be het for clown. If the male throws a normal gene and the female throws a clown gene, the resulting offspring will look like a normal but be het for clown. If both the male and female throw the normal gene, the resulting offspring will look like a normal and will in fact be a normal. If both male and female throw the clown gene, the resulting offspring, having two copies of the clown gene will be a clown.

The issue is that three out of the four scenarios will look like a normal ball python. Only two of the three will actually be carrying the clown gene and the other will not, hence 66% chance het for clown. That is how it plays out on a punnett square.

The reality is that there is no way of knowing if any, or all, or none of the three normal looking babies are carrying the clown gene until they are grown to maturity and proven out. Once again the odds will play a part. So even if they are het it could take more then one breeding attempt to hit the combination that proves it is truly het.

I hope that helps.