This tab of the Barcode Editing Screen allows you to setup margins, border and crop marks of the barcode image. Changes apply immediatly to the preview. Note that you can conveniently change values with the mouse - point the mouse cursor of a given field and hold the left button. Then move the mouse left or right to decrease or increase the value.
Margins define left, right, top and bottom spacing of the barcode. Crop marks are off by default. You can enable them for easier cropping of the barcode.