Purebred female Dalmatian full grown, only 39 lbs?

I've been reading around and I found one site stating that the Females range from 30-45 lbs. But I am pretty sure that site wasn't a good source and everything else I read said 45-50 lbs, for the female. Her parents were both purebred Dalmatians and both average Dal size, and she wasn't the runt. She just had her annual exam and I asked her vet if she would get any bigger and she said not likely. She turned one in May. I don't love her any more or less either way, I actually think it's neat that she's so small. And she's so cute. I'm just confused. lol. Anyone have any ideas as to why she's so small?