Surround Show as pop-up menu: Sets the surround format. The choice you make automatically updates the remaining pop-up menus in the Input pane.
Surround Initialize buttons: Choose between the default setup, the ITU (International Telecommunications Union) standard, and the WG-4 standard.
Surround Input pop-up menus: Sets the physical input for each active position in the selected surround format. Inactive positions have their input pop-up menu dimmed.
Download the guides:
Logic Pro User Guide: PDF
Logic Pro Effects: PDF