The confusion isn't over the attribute maximum, it's the part where the spell's Force must match the (augmented) value of the attribute. Does it mean the value before or after casting? There are weird consequences either way. If you use the value before casting, then drain values are screwy: It's easier to raise 6->9 than 7->9, although in practice the drain value will be trivial anyway. However, if you use value after casting, the spell is extremely difficult to use with sustaining foci. Overall, I think there are fewer problems in practice with using the value before casting, but it's not ideal.