Question for the experts - Unmapped Texels & Unmapped Texel Memory

Hi everyone,

Had a quick question. When examining a lightmap I noticed there are meshes with 0% Unmapped Texels and some with 100% Unmapped Texels. We also have a bunch in the middle.

What should we be shooting for? Is one really bad? The other great? Should we be making the UV lightmap when importing the mesh?

Any help explaining what we should be shooting for, what the above means and how to fix it would be greatly appreciated.

Thanks in advance for the help.