The "Last updated" field must be a custom column added to the library.
Sharepoint only tracks Created and Modified date fields. It must have been
added by the site owner (or someone else with the right permissions) or the
library itself may be based on a custom definition.
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> I'm using Sharepoint Server 2007 and I have document libraries that contain
> columns labelled "last updated" and "modified". They both contain dates, but
> what is the difference between the two?