Here: http://xenforo.com/help/permissions/
"you may specific permissions" should be "you may specify permissions" or "you may use/create specific permissions" etc.
Node Permissions
In addition to specifying permissions for user groups and users, you may specific permissions on specific nodes. Like before, these can be applied to user groups and users.
"you may specific permissions" should be "you may specify permissions" or "you may use/create specific permissions" etc.