The One Mind, or mirror (Realm of Principle), is more than the total of all things (Realm of Things) in the world.
The phenomena rely on the the principle (One Mind) to exist, but the principle is more than just the sum of those parts.
Hence, everything in the world is constituted from the One Mind, which is the Buddha Mind. But the One Mind is not just all the things of the world; it is more than that