Durga Mata is the power of both the Sat and Asat?

Question

The word of Durga Saptashati is that Durga Mata is the power of both the Sat(Real) and the A-sat (non-existent).

But the unreal does not exist. So how she is power of unreal?

Answer 1

Unreal means "Maya" and maya does exist.

“maayaa.n tu prakR^iti.n vidyaanmaayina.n cha maheshvaram.h | tasyavayavabhuutaistu vyaapta.n sarvamida.n jagat.h |” (Swetasvatara Upanishad 4:10) “Know then Prakriti (nature) is Mâyâ (art/illusion), and the Maheshwara the Mâyin (maker); the whole world is filled with what are his members (forms)”.

Maa Durga as the Shakti of Sat.:

अहं पञ्चभूतान्यपञ्चभूतानि । अहमखिलं जगत् । वेदोऽहमवेदोऽहम् । विद्याहमविद्याहम् । अजाहमनजाहम् । अधश्चोर्ध्वं च तिर्यक्चाहम् । अहं रुद्रेभिर्वसुभिश्चराम्यहमादित्यैरुत विश्वदेवैः । अहं मित्रावरुणावुभौ बिभर्म्यहमिन्द्राग्नी अहमश्विनावुभौ । अहं सोमं त्वष्टारं पूषणं भगं दधाम्यहम् । विष्णुमुरुक्रमं ब्रह्माणमुत प्रजापतिं दधामि । अहं दधामि द्रविणं हविष्मते सुप्राव्ये यजमानाय सुन्वते॥३-६॥ 3-6. I am the five elements as also what is different from them. I am the entire world. I am the Veda as well as what is different from it. I am the unborn; I am the born. Below and above and around am I. I move with Rudras and Vasus, with Adityas and Visvedevas. Mitra and Varuna, Indra and Agni, I support, and the two Asvins. I uphold Soma, Tvastir, Pusan and Bhaga, The wide-stepping Vishnu, Brahma, Prajapati. To the zealous sacrificer offering oblation And pressing the Soma-juice do I grant wealth; I am the state, the Bringer of Wealth; Above it all, place I its protector. (Devi Upanishad).

As Maa Durga liberates the atman from this sansara of maya, she is also the shakti of A-Sat.:

"prapadye sharaNa.n devii.n du.ndurge durita.n hara | taa.n durgaa.n durgamaa.n devii.n duraachaaravighaatiniim.h | namaami bhavabhiito.aha.n sa.nsaaraarNavataariNiim.h |” (Devi Upanishad 1:28) “Beyond Her is nothing; renowned is she as Durga; feared of life,I bow to Durga, Bulwark against all sins; the Pilot who Steers me across the sea of worldly life”.

I hope this clarifies your queries.