Fix typo

doc/org.texi

@@ -5810,7 +5810,7 @@ timer is reset to 0.  When called with a @kbd{C-u} prefix, reset the timer to
 specific starting offset.  The user is prompted for the offset, with a
 default taken from a timer string at point, if any, So this can be used to
 restart taking notes after a break in the process.  When called with a double
-prefix argument @kbd{C-c C-u}, change all timer strings in the active region
+prefix argument @kbd{C-u C-u}, change all timer strings in the active region
 by a certain amount.  This can be used to fix timer strings if the timer was
 not started at exactly the right moment.
 @end table