If reading in Placidus: I’ve noticed that in some people’s charts, certain houses are really big while some are tiny. Why is that?

For example, if looking at my chart in Placidus, the houses are about the same size each and look pretty even. In my boyfriend’s chart, his 7th house is huge, almost double the size of my houses. Then, his 10th house is tiny, with hardly any room for a placement.

Why is that?