Do you mean when they've just eaten a 30 gram meal? Or when they've just pooped? Or right after they finished drinking water?
Sounds like yours are "their size." Unless they are so skinny as to be triangular, or so fat as to have bulging sides when they're not digesting, there's really no "exact" way to tell what is "ideal" for any corn or creamsicle. Some are naturally thinner or thicker than others. There's no "ideal weight for a certain age" standard.