Luggage that is 62 linear inches is luggage that totals 62 inches when the height, width and depth of the bag are combined. Any combination of the three numbers that adds up to 62 meets this definition.
To measure a bag for the linear total, first measure the height and the width, which will not change. Then measure the bag after it is packed, as an overly full bag is often deeper than one that is empty. Add these three numbers together to find the bag's linear measurement, and adjust the depth if necessary. Most airlines limit checked bags to 62 linear inches.