大方廣佛華嚴經疏 6.18

6.18

二中，隨憶念言，略有二意：一隨念何佛，如名應之；二隨念有淺深，令見佛有麁妙，此於現身得解脫也。

In the second, the phrase "according to their mindfulness" has briefly two meanings: first, whichever Buddha they are mindful of, he responds according to that name; second, mindfulness has depths and shallows, causing them to see the Buddha as coarse or subtle; this is obtaining liberation in manifesting the body.