"You should strive to keep mass close to 0.1..." Why?

The [documentation] [1] in Unity states: ***"You should strive to keep mass close to 0.1 and never more than 10. Large masses make physics simulation unstable."*** Someone in [this][2] thread, used a value of 1500 for a car and seems to work out well. In regards of the docs as quoted above. Why? Why is so significant with ***"0.1"***? [1]: https://docs.unity3d.com/Documentation/ScriptReference/Rigidbody-mass.html [2]: http://forum.unity3d.com/threads/50643-How-to-make-a-physically-real-stable-car-with-WheelColliders