This is pretty handy stuff to know for Muto, as previously I'd always thought that each time a spell added +1 size beyond size 1, it would cost a mag. I see why that is not the case, and sheesh it really changes growth spells. I'll have to rework the MuAn and MuCo spells I created recently.
So if a spell paid an extra +4 mags to change a creature's size that is equivalent of shift of 12 size ranks (4 mag x3 size ranks)?
+1 is base effect, +4 size is +1 mag, +7 is +2 mags, 10 is +3 mags, and 13 is +4 mags.