Epson CX6500 Reference Manual page 315

Note:
When the output size of the scanned image is already decided, select an appropriate setting
from the Target Size list. A marquee proportional to the measurements of the Target Size
setting appears in the Preview window. You can move this marquee to the area of the
image you want to scan. For more details, see the online help.
Specify the Adjustments settings, if necessary. (You may need to scroll to the bottom of the
screen.)