A pentagon has five corners. I didn't get a pentagon in the game; I got a pentagram which has 10 corners.
Actually, because the shape has not only five corners, but five vertices of the inner pentagon as well, a pentagram has 10 corners. It is like five triangles placed around a 5-cornered pentagon. A pentagram keeps the 5 corners from the pentagon and adds each of the points of each triangle which are also corners, albeit much smaller ones than in the pentagon.