With one "mirroring item" page item you can mirror the whole section or only one page item from the specific section. If you wanted to mirror more than one different page items from the same section, you have to create new "mirroring item" and do the mirroring process again.
Content / Pages
How to mirror items
Mirroring items will make your work easier when you want to have same content on more places.
When you want to mirror some page item you have to know it's "path" in the administation. This path is folded like this: Page Section Page item
When you want to edit a mirrored item then you have to follow this path. The changes will take effect on every page where did you mirrored it.