The first set of numbers is the thickness of the wick, the larger the number, the thicker the wick. The second set of numbers is the speed at which the string goes through the wicking machine gear, the faster it goes through, the tighter the wick and the slower the burn. The third set of numbers is the code for the temperature of the Wax as the wick goes through the various gears. Most suppliers have a chart or guide such as: http://www.tayloredconcepts.com/wicks.htm http://www.peakcandle.com/category/Wicks/Zinc-Core-Wicks.aspx Dave