The atman itself seems to be smaller than the smallest, greater than the greatest. If you say tiny, the atom is tiny. And vast earth or galaxy, these are names and forms. They seem to transfer their qualities exactly like that. So all of the shunka explains again in one sentence, that mad that's the way.
Swami Sarvapriyananda teaches the Katha Upanishad, one of India's most revered texts which is also a part of the Vedas. It is a collection of philosophical poems representing a conversation between the sage Naciketas and Yama (god of death). They discuss the nature of Atman, Brahman and Moksha(liberation).