You have a "reduce" option enabled in the driver.  If you hold the mouse over the actual print and read the size that pops up, that is the exact size that is being sent to the driver.  It is accurate down to the pixel because the size that is showing there is the actual size that is sent to the driver: it gets that data from the image that is actually being sent to the driver.  In other words, there is no way Qimage Ultimate is "off".  It's the driver.  Check your driver and you'll find a "reduce/enlarge" box checked somewhere or maybe a "fit to page" setting checked in the driver.  If any option like that is checked, the driver takes the incoming size and modifies it.  QU has no control over that because the driver is tweaking the size.

I see you are using a 3880.  In the driver under the "Page Layout" tab, make sure "Same as paper size" is selected for the "Output Paper" option.  Many people don't realize that when you change that (if you drop down "Output Paper" and select 11x17 as the size for example), you've just gone into a "reduce" mode.  Ever since Epson put that confusing option in their driver, a lot of people have been caught by that.

Mike