Magic numbers can get a little goofy when you do them this far out. It’s easy to calculate the magic number to guarantee finishing ahead of a team. And you subtract one every time your team wins and the other team loses.
But to clinch a spot you have to eliminate every other team. So, using the playoff magic number, every Brewer win lowers the number against everyone, but a loss by the Reds would lower the magic number to eliminate them, but wouldnt affect the number to eliminate the Giants.
If you’re saying that 9 is the highest magic number the Brewers have to guarantee finishing ahead of all of the teams currently out of playoff position, I think that’s right. But it’s not as simple as the traditional “Any combination of Team A wins and Team B losses.”
Technically the magic number you are using to clinch the division is really the number to guarantee that the Brewers finish ahead of the Cubs. I think it’s safe to assume that the Cardinals (current magic Number of 7) will be eliminated long before the other number gets close to 0.
The magic number to clinch the number 1 seed is less clear because the Cubs, Phillies, and Dodgers are all challengers for that.