This is a representation of the axis mundi. The spiral could have functioned as a ritual. If you have a particular wish, hold it in mind while carving the spiral of creation into a sacred stone. You will then magically create whatever it is that you wish for, since you have aligned your mind with the creative power of the sky. If the spiral and the cup and ring decorations represented the center of the sky and its creative power, then perhaps the larger stone rings themselves also represented the center of the sky and its creative power.
Regular circles represent the whole sky.
A flattened circle is an attempt to represent a picture of the sky in which part of the circle of stars around the center is truncated. We see the full circle overhead heading out from the center, but heading in the other direction toward the horizon the circle is flattened. Ellipses represent a next step. The center of the sky is one foci of the ellipse, the pole of the ecliptic or the point directly overhead is the other foci. But the ellipse misrepresents the shape of the sky.