How to optimize Nanite enabled mesh?

I was hoping the number of repeated mesh would give nanite the advantage. But if even in a more complex scene (The factory environment) with 937,393 triangles and 9,164,979 sum triangles. It’s still unable to gain the advantage. I guess nanite has a more specific use case than I thought. (unless again, I’m doing something wrong)

The editor was giving me warnings that nanite is best used with virtual shadows, not normal shadow mapping. Given I don’t know exactly what virtual shadows do, I gave it a light build just in case. Is that not necessary? I honestly don’t know.