More than one device needs the same information. Editing every single one individually is toilsome.
Multi-Edit is especially useful, when for example a few devices got ordered, and you want to add the order number or something else. Instead of editing every single device individually you can select the affected devices and edit them at the same time, because it is less toilsome.
Select CMDB -> Column -> Current Hardware Type to see if your hardware type is distinguished from Inventory.
Select Hardware and click Multi-Edit.
Select Use Hardware Type from Inventory. This will replace your current Hardware Type with the calculated Hardware Type from the inventory.
Like the Hardware type update item, the current site can also be set for a Multi-Edit. For that, select the hardware under CMDB and press the Multi-Edit button. Select Site Calculate from IP to calculate the Current Site.