To be completely precise, with this many games left things like clinching the division or a playoff spot may not have one “magic number”.
The magic number works with respect to Team A finishing ahead of Team B, and it’s determined by Team A wins and Team B losses.
The magic number of 32 is the Brewers magic number to guarantee finishing ahead of the Cubs. But, theoretically, the Cardinals could get hot while the Cubs fall apart and move into second place, and that would flip the focus for the magic number.
The magic number for clinching any playoff spot would be even more complicated because of how many teams could move into that 7th spot.
But, as long as it’s understood that the target for the magic number could change, using the Cubs for the division and Arizona for the playoff spot would be the correct targets today.
At least the magic number can never go up.