Index: wp-includes/js/media-views.js
===================================================================
--- wp-includes/js/media-views.js	(revision 23066)
+++ wp-includes/js/media-views.js	(working copy)
@@ -3700,7 +3700,7 @@
 			this.$el.toggleClass( 'one', 1 === collection.length );
 			this.$el.toggleClass( 'editing', editing );
 
-			this.$('.count').text( collection.length + ' ' + l10n.selected );
+			this.$('.count').text( l10n.selected.replace('%d', collection.length) );
 		},
 
 		edit: function( event ) {
Index: wp-includes/media.php
===================================================================
--- wp-includes/media.php	(revision 23066)
+++ wp-includes/media.php	(working copy)
@@ -1461,7 +1461,11 @@
 		'search'      => __( 'Search' ),
 		'select'      => __( 'Select' ),
 		'cancel'      => __( 'Cancel' ),
-		'selected'    => __( 'selected' ),
+		/* translators: This is a would-be plural string used in the media manager. If
+		   If there is not a word you can use in your language to avoid issues with the
+		   lack of plural support here, turn it into "selected: %d" then translate it.
+		 */
+		'selected'    => __( '%d selected' ),
 		'dragInfo'    => __( 'Drag and drop to reorder images.' ),
 
 		// Upload