Setting default visibility when creating a group

Hello,

I would like to set the default visibilty for groups to "secret", but I do not know which value to put in the "Visible to" field in the "create group form".

I have noticed that the following values work :

1 for "me only"

3 for "public"

6 for "selected friends"

8 for "selected relationships"

but I do not find the values for "private" and "secreté groups.

Could anyone help me ?

Thank you.