org-provide-todo-statistics

org-provide-todo-statistics is a variable defined in `org.el'.
Its value is

t

Documentation:
Non-nil means update todo statistics after insert and toggle.
ALL-HEADLINES means update todo statistics by including headlines
with no TODO keyword as well, counting them as not done.
A list of TODO keywords means the same, but skip keywords that are
not in this list.

When this is set, todo statistics is updated in the parent of the
current entry each time a todo state is changed.

You can customize this variable.