diff --git a/doc/img/chronochat-1.png b/doc/img/chronochat-1.png
index 97d4b1f..8b22e64 100644
--- a/doc/img/chronochat-1.png
+++ b/doc/img/chronochat-1.png
Binary files differ
diff --git a/doc/index.rst b/doc/index.rst
index 32d07a9..916a044 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -1,7 +1,7 @@
 ChronoChat Manual
 ===================================================================
 
-0. Before open ChronoChat, make sure ndnd is running on your machine, and your default key and certificate have been generated and installed . 
+Step 0. Before open ChronoChat, make sure ndnd is running on your machine, and your default key and certificate have been generated and installed . 
 1. When you open ChronoChat App, you will see a contact panel as shown below.
 
 .. image:: https://raw.github.com/bruinfish/ChronoChat-V2/master/doc/img/chronochat-1.png