Need help with Facebook " Group" settings.?

[Kary G]

I recently joined a group on Facebook where I can buy and sell stuff locally. and for some reason all my friends who are not members of that group can see my posts. I tried going under my privacy settings to see if I could change it but couldn't find a way. Somebody told me there is no way to make the posts private for that group only but when I tried creating my own group it says that making it a closed group means only members will see the posts. Does that mean " group" members or " Facebook" members?

[abraXus]

it means groups members, but only the admins of the group can change that setting - if you arent the admin, you cant change it

and once the group has a certain amount of members, that setting cannot be changed even by an admin