Well, you know how sometimes we count things to help us understand them better? Like counting how many toys you have or how many cookies you want to eat? That's kind of what sociology of quantification is.
It's when people who study society and how people behave try to use numbers and statistics to understand things about people and society. For example, they might count how many people are in a certain job, or how much money different groups of people make.
But sometimes, it's not that simple. Sometimes, people might count things in a way that doesn't really show the whole picture. Let's say you want to know how many people in your class like pizza. If you just ask a few people, you might not get a good idea of how many people really like pizza, because not everyone might answer. Or, maybe people don't like to admit they don't like pizza because they don't want to feel left out.
Sociologists who study quantification are really interested in how people count and measure things, and how that affects what we know about society. They want to make sure that when we count things, we're doing it in a fair and accurate way, and that we're looking at things from lots of different angles so we get a better understanding of what's really happening in society.