It's a bit of a head f***, but that's not what you're doing.
If you were removing one-third of the volume of
juice and replacing it with glycerin, then yes, you would have 24mg juice, diluting the original 36mg juice by one-third. But by ADDING one third of the volume in glycerin WITHOUT removing any juice, you reduce the nic content by 25%.
The glycerin when in the syringe equals 1/3 of the volume of the un-doctored juice, but makes up 1/4 of the volume once it's mixed in.
Going to stop now before I confuse myself.
Kev