Neighbourhood-level inventory changes week to week as listings come on and sell, faster than any static figure could stay accurate, which is why the board reports supply at the citywide level rather than by area.
The practical way to get a real count for Greystone Heights right now is to pull current active listings directly rather than rely on a monthly citywide statistic that was never meant to answer that specific question.
Joel can pull the current Greystone Heights listing count directly rather than estimate it from a citywide number. Get your hand-reviewed valuation from Joel Dyck.