It is a mathematical expression of how many people have applied for one place. For example, imagine that the college has 30 places available to offer. However, the college receives 300 applications from people who want to enrol. In that case, they have 10 applications per place. They will have to select 30 of the best students and reject the rest. They cannot accept all of the students. There are too many.

如果你的文章是关于大学录取方面的，应该翻译为“每个专业的报考人数比例”