It means 1 unit that you see represents 100 units of the actual size 1" (1 inch) = 100" or; 1" = 100' (100 feet) 1" = 100 yards 1" = 100 miles or; 1 centimeter = 100 cm 1 cm = 100 meters 1 cm = 100 kilometers Whatever picture or drawing you are looking at, each unit you measure on that picture is 100 units (as defined by 1 ? = 100 ?)