What do the four powers of The Mother signify?

The four Powers of the Mother are four of her outstanding Personalities, portions and embodiments of her divinity through whom she acts on her creatures, orders and harmonises her creations in the worlds and directs the working out of her thousand forces. For the Mother is one but she comes before us with differing aspects; many are her powers and personalities, many her emanations and Vibhutis that do her work in the universe. The One whom we adore as the Mother is the divine Conscious Force that dominates all existence, one and yet so many-sided that to follow her movement is impossible even for the quickest mind and for the freest and most vast intelligence. The Mother is the consciousness and force of the Supreme and far above all she creates. But something of her ways can be seen and felt through her embodiments and the more seizable because more defined and limited temperament and action of the goddess forms in whom she consents to be manifest to her creatures.

Ref: The Mother with Letters on The Mother