Not quite sure what mathematics you are looking for.
The center bore is meant to fit over the hub pilot simply to align the wheel to the hub. Once the lug nuts are in place and torqued properly, the hub pilot has done its job.
On wheels with larger center bores that the hub pilot, a centering ring is used to ensure the wheel is centered. Wheels can be safely mounted without a ring as long as the wheel is centered on the hub.
You could say it is important for safety because if the wheel is not centered, there will be an unbalanced situation that can cause vibration, or worse. But not critical for bearing the load of the vehicle.
How is the load handled between a car and its wheel?
The Skinny on Hub Centric Rings