If a document contains more than one value on a Keyword Type, and you want to retrieve cross-referenced documents from that document, you can elect to retrieve documents that meet the criteria for just one, for more than one, or for all of those values.
For instance, a document has the Keyword Type First Name that contains two values: Frank and Sarah.
If the document is configured to retrieve cross-referenced documents that match the First Name Keyword Value, and you double-click to retrieve cross-referenced documents, you can choose to retrieve those that match Frank or Sarah.