Best seen in attached 3 screenshots.
It doesn't make sense to me that the four 8 TB drives show as 'Unused' in the pool column (circled in pink).
Relatedly, in the dashboard, it only shows one disk (the SSD, and not the HDDs). This seems wrong too.
This is from a just-purchased iXSystems FreeNAS 2U-12. I didn't create the pool, it came like that from iX.