Calibre deletes news after sending to device

Hi,

So I have downloaded several past issues of News (the economist), and when I connect my Kindle to my computer, Calibre automatically sends the news to the Kindle (which is fine), but then it seems to send the issues (ebook files) from the Calibre Library to the Trash.

I would appreciate any suggestions as to how I can prevent my computer automatically deleting the ebooks after they are sent to my device!