Grid mapped to the chosen label code
Selecting an Avery size code sets the row and column grid and label dimensions used to lay out the design on the Letter-size sheet, matching that product's published geometry - for example Avery 5160 and 8160 are both a 3-column by 10-row grid of 1 in x 2.625 in labels (30 per sheet), while 5163 is a 2-column by 5-row grid of 2 in x 4 in shipping labels (10 per sheet). Because layout is tied to the size code, choosing the correct code before finalizing the design avoids having to recheck alignment if the code is changed afterward.