The Correspondence template uses custom labels for some of its fields: 'Author' for
dc:creator, 'Recipient' for
dcterms:audience, 'Location' for
dc:coverage, and 'Archive' for
dc:source. Since the item table can contain items with multiple different templates, it cannot use a template's custom labels, but has to use the default labels. If you add a
dc:coverage your items' 'Location' will be displayed there.
If you use only the Correspondence template and you'd like to call
dc:coverage 'Location' everywhere, you can change the default label in the 'Vocabularies' pane of the preferences window.