Rabbits come in many sizes and not all rabbits are made equal. Just like human, we have really short and really tall people.. Even for a specific breed like the Netherland Dwarf- they are the smallest breed of rabbits in the world, but that doesnt mean they are all same size. Even within a Netherland Dwarf breed, there are different quality (pet, brood & show) and they vary in size from 800g to even 1.3kg! A bigger dwarf doesnt mean it is not a dwarf.
Before you read on, I need you to understand that Very Small DOES NOT ALWAYS EQUAL TO Very Young. Some rabbit just grow slower than others, even within the same litter, you will find rabbit of extreme sizes. I did have a customer who's male & female (both 900grams) purebreed netherland dwarf bunnies are both brood quality (brood or breeding quality refers to rabbits that are generally nicer than the pet quality, but not up to the show quality standard. Some show quality rabbits do deteriorate in body condition as they age or after birth and hence fall into the brood quality category) gave birth to kids that grew up to adult weighing 800g to 1.4kg!! Purebreed means that last 3 generations of their parents are also netherland dwarfs. The kid that grew up to 1.4kg is still a purebreed netherland dwarf (not a mix breed), but its just bigger boned, such rabbits we term them pet quality. Usually pet quality describes those that fall out of the show quality standard.
Here's I'll show u comparisons of rabbits at different age and will give details on their body structure. Will also give you tips on how to identify their development. All these, based on experience with many many rabbits that crossed our paths over the last decade. You be the judge