What is the meaning of "concentrated solution" in the style of ancient books?

The style of "centralized solution" is to annotate the theories of various schools. The Analects of Confucius and Fan Ning's Chunqiu Zhuan Liang Zhuan and Annotation of Thirteen Classics are representative works of this style, while Du Yu's Chunqiu Zuozhuan Ji Jie does not belong to this style, and its annotation is still Du Jia's words. There are not only solutions, but also theories, notes, lectures, essentials, meanings and biographies, which are widely used in various annotation fields. As far as Biography is concerned, the famous works in Song Dynasty include Zhu's Biography of Poetry, Cai Shen's Biography of Books and Su Zhe's Chunqiu.