There are two dashed lines on all labels on the design interface. This just demonstrates where you would possibly stitch your labels onto your garment or product and will not appear once printed. It is there to help you positioning your designs.
You can check how your design will look by clicking on "Preview and Buy". The design interface will show a computer generated preview of the front and back of the labels as well as the dashed lines. Please ensure that your design is appropriately positioned on the printing area in order to prevent from possible disappointment.
A good tip would be to print out your design at the size of your labels on a piece of paper. This could work as a prototype and you will be able to make sure it looks as you wish.
Inserting text on your label design:
The preview of your design is not the on the actual size of the labels. It looks bigger on your screen than it will look once printed. Make sure your text is big and bold enough by using the ruler at the top and left of the design interface. Since your labels are printed on fabric, it will not look as crisp as it does on the screen.
Check the images above which show the design interface, the computer generated preview and the final product. See the example on how to rotate your design.
Front of the Label (after choosing the size / type / quantity in the "Product Options" section)
Preview of the design after clicking on "Preview and Buy"