cakram ca diksv avihatam dasasu sva-tejo
manvantaresu manu-vamsa-dharo bibharti
dustesu rajasu damam vyadadhat sva-kirtim
satye tri-prstha usatim prathayams caritraih
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
As the incarnation of Manu, the Lord became the descendant of the Manu dynasty and ruled over the miscreant kingly order, subduing them by His powerful wheel weapon. Undeterred in all circumstances, His rule was characterized by His glorious fame, which spread over the three lokas, and above them to the planetary system of Satyaloka, the topmost in the universe.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
We have already discussed the incarnations of Manu in the First Canto. In one day of Brahma there are fourteen Manus, changing one after another. In that way there are 420 Manus in a month of Brahma and 5,040 Manus in one year of Brahma. Brahma lives for one hundred years according to his calculation, and as such, there are 504,000 Manus in the jurisdiction of one Brahma. There are innumerable Brahmas, and all of them live only during one breathing period of Maha-Visnu. So we can just imagine how the incarnations of the Supreme Lord work all over the material worlds, which comprehend only one fourth of the total energy of the Supreme Personality of Godhead.
The manvantara incarnation chastises all the miscreant rulers of different planets with as much power as that of the Supreme Personality of Godhead, who punishes the miscreants with His wheel weapon. The manvantara incarnations disseminate the transcendental glories of the Lord.