When cleaning out old emails from the same sender, e.g., accumulated adverts from Best Buy, doing an inbox search often results in more than one page of them.  Clicking the select box at the top checks everything on that page and brings up the 'Select everything' option.  Clicking that brings up "Everything in this view is selected" after which hitting the delete button brings up the title of this query, "You're about to delete all of the messages in this view" along with an 'EMPTY' button.