Index: wp-content/themes/twentythirteen/css/editor-style.css
===================================================================
--- wp-content/themes/twentythirteen/css/editor-style.css	(revision 24580)
+++ wp-content/themes/twentythirteen/css/editor-style.css	(working copy)
@@ -397,6 +397,10 @@
 	padding-left: 120px;
 }
 
+.post-format-audio.mceContentBody {
+	max-width: 484px;
+}
+
 .post-format-audio a {
 	color: #fbfaf3;
 }
@@ -411,7 +415,7 @@
 	float: left;
 	width: 120px;
 	display: block;
-	height: 100%;
+	height: 97%;
 	position: absolute;
 	left: 0;
 	top: 4px;
@@ -499,6 +503,7 @@
 }
 
 .post-format-status.mceContentBody {
+	max-width: 569px;
 	font-size: 24px;
 }