The manual includes the following:

To keep the overview over the fraction of subtasks that are already
completed, insert either ‘[/]’ or ‘[%]’ anywhere in the headline. These
cookies will be updates each time the todo status of a child changes. For
example:

     * Organize Party [33%]
     ** TODO Call people [1/2]
     *** TODO Peter
     *** DONE Sarah
     ** TODO Buy food
     ** DONE Talk to neighbor

This seems to mean that if I enter the following into an org file:
** TODO test3 [/]
*** TODO test 1
*** TODO test 2
*** TODO test 3
the [/] should be updated as I mark the sub tasks done. This doesn't work
for me.

I can get [/] and [%] to work with checkboxes. Is there some variable that I
need to set to get this to work?

Dave Ellis