diff --git a/doc/admin-guide/plugins/header_rewrite.en.rst b/doc/admin-guide/plugins/header_rewrite.en.rst
index 12f9b4acc25..7efcbbb65ac 100644
--- a/doc/admin-guide/plugins/header_rewrite.en.rst
+++ b/doc/admin-guide/plugins/header_rewrite.en.rst
@@ -470,7 +470,7 @@ RANDOM
 
     cond %{RANDOM:<n>} <operand>
 
-Generates a random integer between ``0`` and ``<n>``, inclusive.
+Generates a random integer from ``0`` up to (but not including) ``<n>``. Mathmatically, ``[0,n)`` or ``0 <= r < n``.
 
 STATUS
 ~~~~~~