Before there is total confusion this is the whole world that Cali lives in.
People live in a society where they are "rated" "ranked" whatever, when they are born. This is based on what the parents are ranked. Say the mom is a 2 and the dad is an 4. Well the two numbers equal 6 and 6 divided by 2 is 3. So the child would be born a 3. As soon as they turn 18, they are sent through an exam to determine what they are rated. So if you were born a 3 and you went through an awful puberty you might be a 3 to 1. It's all based on how you look in this society. You can only be with someone 2 ranks above or below yours and if not, you are punished by losing a mark. You get three before you are dropped a rank. If you hit 1, you are pretty much dead. You serve no purpose to the society and your words aren't taken over the other ranks. You work as a farmer, or in a factory. Nothing better. If you're lucky you are a maid.