When I choose Booklet imposition on a job with two A4 pages, the imposed file has an extra A3 sheet as if the original had 4 A4 pages. Why is this?

Pyxis Imposed requires a minimum of 4 pages to impose a booklet. If you try to impose a file with less pages, two for example, the application will automatically add two additional pages at the same size as the original. If you click impose with one page document open, 3 further pages will be added.