I really don't know where they get the Wattage ratings on those coils... @ 0.5 Ohms, 15W is 2.7V, and 60W is 5.5V... both well within the operational limits of the Subbox. As FXRich posted above, the Wattage you use is going to be determined by the juice in the tank. Some juices NEED higher Watts, some don't. I have some juices that taste like garbage once I pass 15W, regardless of the tank... and in the same tank, a different juice needs 25W to taste it's best... As always, start low on Wattage, vape, turn it up a bit, vape, repeat... once you get a slightly burnt taste, back it off about 0.5W and that is the sweet-spot for that coil/juice combo. Think of vaping like driving... just because your car can do 120mph doesn't mean you have to pull out of your driveway at 120mph! Start slow and work your way up to the "speed limit" of the juice, so to speak