My b2evolution Version: Not Entered

Hi,
I installed 1.9.3 on my server. And I created two new users, test1 and test2. Also created a new blog, TBlog. I set test1 and test2 as the member of TBlog. Both test1 and test2 can post blogs on TBlog. But, they can edit and delete blogs from eatch other. Based on document, the member accessing right, only can post and edit their own writings. Is it my mis-understand? I need the users, whom in same group or blog, can not edit posting from the other, and only can edit his own writing. How to do that?
Thank your help!