Update doc

lib/includes/nghttp2/nghttp2.h

@@ -3566,7 +3566,7 @@ NGHTTP2_EXTERN int nghttp2_session_upgrade2(nghttp2_session *session,
  * Serializes the SETTINGS values |iv| in the |buf|.  The size of the
  * |buf| is specified by |buflen|.  The number of entries in the |iv|
  * array is given by |niv|.  The required space in |buf| for the |niv|
- * entries is ``8*niv`` bytes and if the given buffer is too small, an
+ * entries is ``6*niv`` bytes and if the given buffer is too small, an
  * error is returned.  This function is used mainly for creating a
  * SETTINGS payload to be sent with the ``HTTP2-Settings`` header
  * field in an HTTP Upgrade request.  The data written in |buf| is NOT