Setting the pane to “Bottom” means that you see fewer messages in the folder, but you see more details about those messages and more of their content in the Reading pane. This option applies to the Reading pane in whatever folder you are in, so you can’t set different positioning settings for different folders. Your options are to change the position to “Down” (so Outlook shows the Reading pane below the message) or “Off,” which will hide the Reading pane.
