Finally, there is depth with forward and back. In the space program these were called pitch, roll and yaw. Imagine a three dimensional graph with gradations in minus and plus around a central point. The Maharal utilizes a box with its six sides. Now that immutable reference point in the middle of our 3D graph is the number seven.
All existence revolves around and relates to that point.
Seven is the fulcrum around which all physical reality does its thing. Seven is the core of reality. The definition of physical items includes all those numerical parameters of size. The description of physical movement is all those plus and minus numbers in the six directions. Number seven doesn't have any of that.