It's just about classed as sub-ohm. Sure, the coils are 0.6 but the overall power is not true cloud-mania.
Let's say it vapes at 25 watts on average, then that's like 12.5 watts using twice as strong
juice.
Half a pack a day is not many cigarettes. 12mg at 25 watts is too much for almost every type of user although no two people are the same.
One has to factor in the strength of the liquid and the amount consumed. How much does the tank hold?
If you only vaped 1 tank and took less than 10 puffs per vape, then 12mg might be OK.