Where does the wine that Olivander casts from Harry's wand come from?

In Harry Potter and the Goblet of Fire, chapter The Weighting of the Wands Olivander conjures wine with Harry's wand:

Mr. Ollivander spent much longer examining Harry’s wand than anyone else’s. Eventually, however, he made a fountain of wine shoot out of it, and handed it back to Harry, announcing that it was still in perfect condition.

As we all know food cannot be conjured out of nowhere - first exception of Gamp's law. Wine still counts as food or at least a derivate of food (grapes or any fruit in general).

So where does it come from?