Index: wp-content/themes/twentyten/loop.php
===================================================================
--- wp-content/themes/twentyten/loop.php	(revision 15811)
+++ wp-content/themes/twentyten/loop.php	(working copy)
@@ -79,7 +79,7 @@
 						<div class="gallery-thumb">
 							<a class="size-thumbnail" href="<?php the_permalink(); ?>"><?php echo $image_img_tag; ?></a>
 						</div><!-- .gallery-thumb -->
-						<p><em><?php printf( __( 'This gallery contains <a %1$s>%2$s photos</a>.', 'twentyten' ),
+						<p><em><?php printf( _n( 'This gallery contains <a %1$s>%2$s photo</a>.', 'This gallery contains <a %1$s>%2$s photos</a>.', $total_images, 'twentyten' ),
 								'href="' . get_permalink() . '" title="' . sprintf( esc_attr__( 'Permalink to %s', 'twentyten' ), the_title_attribute( 'echo=0' ) ) . '" rel="bookmark"',
 								$total_images
 							); ?></em></p>