Ok...I have a 30ml bottle of 30mg PG. If I mix that 50/50 with PG, then I will have 15ml nic right? If I then mix that with any equal amount of VG/PG, the nic level will go down to around 7 correct? If I want to keep my nic level around 15, then I need to keep my nic liquid at 30? I wanna get all this right before I actually start using it.