Invite Only group posts appear in the Non Signed up section

Hi There!

I am new to this so this might be a redundant question.

But, i have posted an image in a "private" group. At least thats what i thought.

The group has the "invite only group" setting, but after sharing the image, it shows up in the non-signed in section below the "Log in to your account" and "dont have an account" sections in "recent albums".

How can i create a private group in which posts are not shared with everyone but only with approved members of that group?

Thanks

Edwin