Here's an example... Say I want to make 10 ml of 6 mg/ml
juice at 50/50 pg/vg with 10% flavor.
If I start with 12 mg/ml nicotine all in pg, the program I am using tells me I need to add -0.6 ml of pg to my juice. I can't add -0.6 ml of something, which is impossible, so I know that won't work. (IOW there is not enough room for all the stuff I need to add). Different programs deal with an impossible mixture in different ways.
If I had mixed up my diluted nicotine base as a 50/50 pg/vg mixture I would have enough room because the diluted stock would already be closer to my desired final pg/vg ratio.
Now, 10% flavor is okay for me, because I like my flavors at about that level, but many people like them a bit stronger. It all sort of depends on what you are going to be doing. Whatever you decide to dilute your nicotine to, I'd recommend only diluting some of it (maybe 1/4-1/2 of whatever amount you got). After you make a few mixes you will have a better idea if that is a good working concentration for what you want to do.
