The Anti-Monitor turns the Known Multiverse into energy then absorbs it, before the Monitor and Anti-Monitor clashing cancels each other out and turns them both into energy, which Maxwell takes to remake the entire Multiverse.This is pretty simple all up. The multiverse is a Scribblenaut-esque version of the DC multiverse with 52 universes (prior to it becoming infinite again). The total mass energy of the observable universe is
2.55e49 tons (or 2.31332108699999996e+52kg). The Anti-Monitor absorbed the energy of all 52 universe and Maxwells notebook absorbed that energy again to remake it.
E = mc^2
= 2.31332108699999996e+52 X 299792458^2
= 2.07910931e69 X 52
= 1.08113684e71/10^44
= 1.08113684 NINAFOE
Final Results
Maxwell remakes the multiverse = 1.081 NINAFOE
And to cap it all off...Crisis On Infinite Earths happened in the Scribblenauts version of the DC Multiverse. Meaning even if there was just 52 universes the feat might still be infinite.