The Smelting leveling guide is generated by combining the lowest cost recipes for the given level ranges. The default ingredient costs are weekly averages of multiple servers. For more accurate results, you can enter your own prices and exclude the ingredients you don't wanna use on the price and ingredients customization page.
After reaching the maximum level, you can continue to earn experience and gain aptitude levels. For each Smelting Aptitude Level, you'll earn 3 reward boxes. To enable the Aptitude mode, simply turn it on below.