The solverVelocityIterations affects how how accurately Rigidbody joints and collision contacts are resolved. Overrides Physics.defaultSolverVelocityIterations. Must be positive.
Increasing this value will result in higher accuracy of the resulting exit velocity after a Rigidbody bounce.
If you are experiencing issues with jointed Rigidbodies or Ragdolls moving too much after collisions you can try to increase this value.
See Also: Rigidbody.solverIterations.