Explanation for Puella Cosmology:
In Homura Tamura, it was revealed that there is infinite numbers of Homura's. What we overlooked was the fact that they are already that way to begin with, not the fact they were the result of Homura time travel sheniegans.
Let's just say all the Infinite Homura made a contract with Kyubey at the same time. As we already knew, when Homura went back in time, it creates a new timeline. So when all those the Infinite Homuras travels back to past, a new infinite numbers of universes were created in process, an entirely 2-A Multiverse. The number of the Multiverse will keeps growing each times those Infinites Homura travels back to past, and even if you want to argue that not all Homura travelled back to past, Infinite minus one is still Infinite.
There is also more interesting fact about Cosmology in PMMM.
Magia Record revealed that even an insignificant action such as "kicking a pebble" can creates a new timeline. This was backed up in Homura Tamura where Tamura stumbled in the same universe/timeline as one of alternate version of her (the prankster Homura). When both went out form that timeline, the numbers of prankster Homura has significantly increased (when originally they were just one of her throughout the Multiverse). This implies that even a single timeline/universe can branches off into their own separates set of Multiverse of their own.
And needs I remind you that this was before Madoka's ascension into Law of Cycle.