Epson GT-30000 - Manual (Page 20)

Scanner Settings
16
Width The width of the scan area in the selected measurement units.
Height The height of the scan area in the selected measurement units.
Pixels, Inches,
Centimeters Select the desired measurement units from these three choices. Any
measurements present are converted to the units you select.
Snap Select this check box if you want the scanning area to automatically adjust to an
even measurement boundary (0.1 cm, or 1/8") when dragging the handles in the
preview area. Clear this check box if you want the scanning area to remain
exactly as you define it.