I have the following warning:

** 
* Warning ** * CalcSurfaceCentroid: 5 Surfaces have the Z coordinate < 0.
**  *   ~~~   ** * ...in any calculations, Wind Speed will be 0.0 for these surfaces.
**  *   ~~~   ** * ...in any calculations, Outside temperatures will be the outside temperature + 9.750E-003 for these surfaces.
**  *   ~~~   ** * ...that is, these surfaces will have conditions as though at ground level.

What does what this mean??

I have the following warning:

* Warning * CalcSurfaceCentroid: 5 Surfaces have the Z coordinate < 0. * ~~~ * ...in any calculations, Wind Speed will be 0.0 for these surfaces. * ~~~ * ...in any calculations, Outside temperatures will be the outside temperature + 9.750E-003 for these surfaces. * ~~~ * ...that is, these surfaces will have conditions as though at ground level.

what this mean??