By the statement about the subtle space-point which is the locale for the Atman in the heart, it follows that all around the point there is the heart. That is also a small locale.
The Upanishads use the two words ‘daharaM’, ‘dahraM’ for this. Both mean ‘small’.
In later times this ‘dahraM’ became ‘dabhraM’.
The heart and the Atma-sthAnaM (location for the Atman) within are called ‘daharaM within daharaM’ and ‘dahraM within dahraM’ in the Upanishads (Ch. U. VII- 1; Taittiriya AranyakaM XII – 16).
The Absolute Reality of Brahman which is permeating everywhere ‘is’ in such a small space.
The entire universe is the cosmic expansion of the VirAT-purushha.
The heart of this Cosmic Purushha is Chidambaram.