Default copies value should be '1'.

chrome/browser/resources/print_preview/data/ticket_items/copies.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 cr.define('print_preview.ticket_items', function() {
   'use strict';
 
   /**
    * Copies ticket item whose value is a {@code string} that indicates how many
    * copies of the document should be printed. The ticket item is backed by a
@@ skipping 29 matching lines @@
     },
 
     /** @return {number} The number of copies indicated by the ticket item. */
     getValueAsNumber: function() {
       return parseInt(this.getValue());
     },
 
     /** @override */
     getDefaultValueInternal: function() {
       var cap = this.getCopiesCapability_();
-      return cap.hasOwnProperty('default') ? cap.default : '';
+      return cap.hasOwnProperty('default') ? cap.default : '1';
     },
 
     /** @override */
     getCapabilityNotAvailableValueInternal: function() {
       return '1';
     },
 
     /**
      * @return {Object} Copies capability of the selected destination.
      * @private
      */
     getCopiesCapability_: function() {
       var dest = this.getSelectedDestInternal();
       return (dest &&
               dest.capabilities &&
               dest.capabilities.printer &&
               dest.capabilities.printer.copies) ||
              null;
     }
   };
 
   // Export
   return {
     Copies: Copies
   };
 });