Question, what is the reason for the ruler at the top of the edit page, not showing 24 inch, or 36" etc. Whatever paper size is chosen. You can see the full ruler on the left.
The ruler shows what the driver gives it. There's no ambiguity as to what the driver is doing with Qimage: just look above the preview page and Qimage will list "Page: " followed by the size of the page as defined by the driver. 23.766 is a typical width for an Epson using 24 inch paper if you don't have borderless enabled.
Regards,
Mike