Information that can be edited here depends on whether the item is linked to an article or not.
Meter [Virtual]: This is used when meter readings for an asset need to be accumulated to a connected item.
If the item is connected to an article, these fields will be locked to prevent editing, since the values in these are taken from the article card:
Article
Serial number
Group
Type
Supplier
Manufacturer
Any other extra information from the article group
+ Document: Documents can be uploaded to the item.