When you purchase a filled cartridge and the nicotine rating is say 6mg's of nicotine does that mean when the cartridge is empty you have consumed 6mg's of nicotine or is that per drag? When you are dripping and buy the 6mg e juice and you put three drops say in the blank cartridge does that mean that there is a total of 18mg's in the cartridge? I'm new to this and would really like to know how the nicotine rating works with the pre filled and with the blank cartridges while adding the e juice. Also, would you rather go with the DSE 901 or the Yeti 510? I can't make up my mind.