diff --git a/slides/sections/4.md b/slides/sections/4.md
index b2c6f31..842c4f7 100644
--- a/slides/sections/4.md
+++ b/slides/sections/4.md
@@ -71,7 +71,7 @@ Half Sample Mode
   \draw [blue!50!black, fill=blue] (-0.6,-0.1) rectangle (-0.8,0.1);
   \draw [blue!50!black, fill=blue] (-0.1,-0.1) rectangle (0.1,0.1);
   \draw [blue!50!black, fill=blue] (1.1,-0.1)  rectangle (1.3,0.1);
-  \draw [blue!50!black, fill=blue] (2  ,-0.1)  rectangle (2.2,0.1);
+  \draw [blue!50!black, fill=blue] (2,-0.1)  rectangle (2.2,0.1);
   \draw [blue!50!black, fill=blue] (2.7,-0.1)  rectangle (2.9,0.1);
   \draw [blue!50!black, fill=blue] (4,-0.1)    rectangle (4.2,0.1);
   % future nodes