Wisconsin does have same day registration.
However(1), in order to achieve even 60% turnout, there would have to be 5,481,281 registered voters. That would be up from the 3,684,726 number stated on the webpage.
However(2), the 3,684,726 number stated on the webpage may just be wrong.
However(3), the same site shows voter registrations as of 11-1-2020: https://elections.wi.gov/sites/elections.wi.gov/files/2020-11/RegisteredVotersByCounty_11-01-2020.xlsx
And that link shows 3,684,726 registered voters.
Dont worry Wisconsin will change that website asap and fix the right number in there so the math works, just like the number of extra votes needed.