Use ProSurfaceParamEval how to the closest point inside the surface contour (face) specified

hello !
when input red point xyz and surface ,out uv,then put uv to ProSurfaceXyzdataEval,Why do two points have the same value?
my code:
ProError EvalClosestPoint(ProPoint3d xyz,ProPoint3d xyzPnt) {
ProUvParam uv;
ProError status;
status=ProSurfaceParamEval(m_owner, m_surf, xyz, uv);
status= ProSurfaceXyzdataEval(m_surf, uv, xyzPnt, NULL, NULL, NULL);
return status;
}
thank you!


