成唯識論演祕 4.273

4.273

本明心等而有所依。今者先徵所依等義，名從下也。解文同徵故云應爾，故後解中先解二別，後明心等具依多少。

Originally, it explains that mind and the like possess a basis (āśraya). Now, first questioning the meaning of basis and so forth is called '[explaining] from below'. The explanatory text matches the question, hence it says 'should also be like this'. Therefore, in the subsequent explanation, it first explains the two distinctions, and afterwards clarifies the number of bases possessed by mind and the like.