When you’re mapping xpaths to fields, assume that what you’ve entered in “Xpath to posts” above is being prepended to whatever you enter here. So the context you’re operating in is at the item level now rather than the feed level.
But, you can go back up to the channel level with Xpath’s parent selector: “..”
So if I understand your example, to get the channel title, you want to enter “../title” in the field. I’ve used this successfully in my own use of the plugin.