Some people who have a raised a lot of babies and keep record of their growth. This snake is in the average yearling range.
However there are other factors that can make a snake smaller than it's age suggests it should be. If it wasn't fed very much it could make a snake grow much slower and so stay smaller. Also genetics. Some snakes are just plain bigger or smaller than average.
I have a three year old male who is just now starting to grow a bit. He looked like a yearling for long time. I fed him just as much as the others. But he was just a slow grower.