[bredren]

This is the thing. It costs a lot to get a nice vape and it is also not cheap from an effort / money to maintain compared to cigs which you just throw on the ground. It is almost a hobby-level undertaking.

People do switch juices all the time so it is common to have different bottles of varying quantities sitting around.

If you're just vaping with whatever you can get your hands on and conceal as presumably teens are, I doubt they have a nice repeatable setup with a trigger counter.

But regardless, there are none of these confusing points in branded cigarettes. One cigarette is one cigarette end of story.