That really isn't a sufficient answer. Heine's really paying attention now, spinning his pen between his fingers but staring at Curtiss.

He ignores the attempt to bring them back to the topic of detention.

"What's the cast for the hex?" Could be verbal, could be mental, could be physical. Heine doesn't make it a habit to read books of hexes (or... books in general), and he can't guess it from just knowing the effects.