The grid in Design and Print Online can be used to help you determine the placement of your text and images on your template, and what size it would be on a printed product. As the grid is dynamic, it will adjust its gridlines based on your template number and zoom level.
For example, 5164 at the default 100% zoom will be divided into darker 1" grid lines, and lighter 1/2" subdivisions. This can be quickly identified by there being four gridlines horizontally, and three gridlines vertically, with some left over for the remaining 1/3".
If the zoom level is reduced, the subdivisions will disappear, leaving fewer and fewer gridlines. This is at 74% zoom:
And again at 30% zoom, where each gridline now represents either 2" or 1 1/3":
As scale increases beyond 100%, there are more subdivisions. At 157% the 1/2" are divided into 1/4", and at 265%, it is divided into 1/5":
At 500%, it divides into 1/10":
Each template will scale differently based on its size, however at 100%, all templates will be divided into 1" gridlines and 1/2" subdivisions, and at 500% into 1/10" subdivisions.
When used with the tips and guides found here, you can accurately recreate what your label will look like before purchasing or printing.