The Nityas or Eternities of Lalita represent the fifteen Lunar days or Tithis of the Waxing Moon. The full circle of the Nityas also represents the 21,600 Breaths a Human Being takes in a full day and night. The 15 Nityas are modifications of Lalita as Red Goddess with her three Gunas and her five Elements of Ether, Air, Fire, Water and Earth. Each Nitya has her own Mantra, Yantra and group of Energies (Shaktis).
The Upanishad says that the Human Body is to be conceived as the Sri Chakra, being the Expression of one’s own Self. The Body is to be regarded as not different from the Atma, the Entire Cosmic System associated with the Body is also the same. This Manifestation rests on Time, Space and a combination of the two. The 15 lunar Tithis are to be regarded as Identical with the 15 Nityas. The sixteenth Kala called Sadakhya should be viewed as one with Lalita or the Supreme Deity Herself, being the 16th day or Full Moon.
“Sri Lalita Sahasranama is a hymn to the Mother Goddess. The ‘one thousand auspicious names of Lalita’ (the beautiful Mother Goddess) appears in 182 in the form of a dialogue between Hayagriva and Sage Agastya at the end of the Uttara Kanda (the later part) of the Brahmanda Purana." -The Encyclopedia of Hinduism