363 squares, of which 221 lie on the way through. The other 39 per cent are wrong turns, and that proportion is what makes a maze hard rather than the size of it: a big maze with few branches is solved at a glance.
There is exactly one route between the way in and the way out, and no loops and no squares walled off from the rest. That is a property of how the maze is cut rather than something checked afterwards, which is what makes the answer sheet the answer rather than an answer.
The snowflake silhouette is cut before the maze rather than stamped over one afterwards. Trimming a finished rectangular maze to a shape leaves corridors sliced open at the edge and stubs of wall floating outside it; masking first means the corridors never knew the outside was there.
The second sheet is the same maze with the route drawn on it. It prints separately, so it can be kept back.