I drip on the mesh thingy in the center ( the bridge). 3 drops every 4 hours means you must not vape that much. I drip 3 drops after about 7-10 puffs.
I have read that a typical cigarette has 1-2 mg of nicotine in it. Your 24 mg of nic juice is mg/ml, so your 15ml bottle has 360 mg of nic. So the 15ml bottle will give as much nic as 180 cigs ( approximately). That being said our bodies may absorb nic differently from vaping as opposed to smoking.
There is approximately 180 drops in a ml. Your juice has 24mg per ml, so 1 ml is equivalent to a pack & a half of cigs.
If my math is off someone will come by and correct me Im sure