The dragon size chart is a general idea so you can get a picture of how big they are. It varies between species of course, that chart would be the growth of a nightmare dragon. So for example. The silver dragon is longer than most, the green is a smaller dragon, the brown is larger. Just try and imagine different builds. For the green, or the pink, imaging a smaller dragon, perhaps a foot shorter and a shorter body. Or for the brown, picture a much bulkier dragon, bigger than the others of his own age. It would be difficult for me to get reference images for each breeds growth stages lol