Usually a pullets first eggs on average are smallish compared to what an adult hen of that breed will lay, if the pullet is in good condition and fed well etc, the size she lays gets gradually larger as she keeps laying, until they hit normal size for her breed ... the charts for the commercial breeds usually say it takes them about 2-3 months. The biggest average eggs they will lay are usually when they start laying again after their first molt. The egg looks like a normal egg, just small (it has a yolk?) Pullets just starting will also sometimes lay all kinds of weird eggs, besides really big ones or small ones, tiny ones without yolks/ wind/ fart eggs, the double yolked ones, shell-less ones etc as they get their system in gear.