Shortening the image from the top down may result in scanning difficulties and affect the integrity of the barcode image. This may lead to longer lines at the check out counter of the shop that sells your product because the image is more difficult to scan.
Naturally it's not uncommon to see shorter of smaller barcode images. This is often seen on products with small packaging. Please contact the supplier of your barcode (GS1) for more info regarding this matter or consult the user manual you received from you supplier.