The System Assets tab shows different information depending on whether you are viewing the actual system itself, or whether you are viewing a level belonging to the system.
If you are viewing the Assets tab for the system, this tab shows all the assets that have been linked to any level of the system. You can see the physical location of the asset, the asset class, and the asset number.
If you are viewing the Assets tab for a level belonging to a system, this tab shows all the assets that have been linked to the level object of the system. You can see the physical location of the asset, the asset class, and the asset number.