What does it mean "Render mesh: 6 fast meshes" and how can we create or modify a solid to have 6 fast meshes

there are several ways to create a solid in Rhino, however, I noticed when the solid was created and you are in the mode of SHADED VIEWPOINT, this note (Render mesh: 6 fast meshes) needs to be mentioned in details of the properties of the solid to be imported to other software. Here’s my question, what is the meaning of the note and how can we create a solid with always 6 fast meshes and if I have any solid with for example 5 fast meshes, how can we modify it?

That refers to the render mesh settings in the file which are accessible in Options>Document Properties>Mesh. The default of ‘jagged and faster’ will produce ‘fast’ meshes in that they display faster by using less polygons. If you make an extrusion object, these will have a special lightweight render mesh not listed as fast which may be what you’re seeing. Use SelExtrusion to test if there are extrusion objects present. You can then use ConvertExtrusion to change it into a polysurface that will then use the global render mesh settings. If you’d like to not use extrusions at all when it’s possible to create them, run the UseExtrusions command and set it to polysurfaces by default.

Does that help?