The milk jugs we get have smaller caps so I can't tell just how small it is but have you tried incubating some that are that small to see if they would hatch, to see if they would be normal chickens rather than deformed and to see if they grow up to be normal sized? I'd be interested. I get smaller eggs now and then, not that small, but I am not good at keeping records, it's a work in progress, so I don't know if the chicks grow as fast as the others. Oh, yes, I did keep an eye on one but it turned out not to be fertile.