Fix typo in 13.02, example code comment (derf)

Change-Id: I2ab683f581b956580d9c6bd68fa14c1c831fe994
modified:   text_src/13.02__vp8-bitstream__coding-of-individual-coefficient-values.txt
diff --git a/text_src/13.02__vp8-bitstream__coding-of-individual-coefficient-values.txt b/text_src/13.02__vp8-bitstream__coding-of-individual-coefficient-values.txt
index f2d8500..8452652 100644
--- a/text_src/13.02__vp8-bitstream__coding-of-individual-coefficient-values.txt
+++ b/text_src/13.02__vp8-bitstream__coding-of-individual-coefficient-values.txt
@@ -53,8 +53,8 @@
      18, 20,
       -dct_cat3, -dct_cat4, /* cat3 = "1111100", 
                                cat4 = "1111101" */
-      -dct_cat5, -dct_cat6  /* cat4 = "1111110", 
-                               cat4 = "1111111" */
+      -dct_cat5, -dct_cat6  /* cat5 = "1111110", 
+                               cat6 = "1111111" */
 };
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 {:lang="c"}