She said "we had a cooking class today" so she's already done it. Is this a mistake in the translation or is she intentionally trolling him?
Based on how the overall interaction went in the first three pages, I assumed she was just trolling him.
My logic was that the guy wasn't aware of when her cooking class actually started, only that she was meant to have one on the day. Which I think makes sense, since he realistically doesn't need to know when any other classes start, only his own art classes.