How much "Polygon Count" affects lightmass build time?

Check out this article if you have not already, its excellent and it speaks to build times near the bottom of the page: CPU Lightmass Global Illumination | Unreal Engine Documentation

Hi there,

I know the more polygons are there for a scene, the more VRam is occupied.
But I have no idea about how much it affects the time needed for a fixed lightmass build setup.
Would anyone clarify please?

Thanks in advance