Attachment to Content Pane always inherits "Pane settings"

I set up a view with a content pane and an attachment. Attachment is attached to the content pane.
For the content pane I set up "Allow settings" (in Pane settings) to manually change the number of items within a panel page.

As long as I don't activate this option, the individual number of items for the attachment are respected. As soon as I active this option, the attachment shows the same number of items as the content pane.
In attachment display "nherit contextual filters", "Inherit exposed filters" and "inherit pager" are set to "no".