The best I can figure out/guess, water vapor in the air gets stuck to PG/VG and becomes visible droplets. Much like your breath into cold air. This undoes rapidly which is why vapor dissipates rapidly. A slight haze remains longer. I was told I was wrong but not why, I don't think the person could explain why. Anyway, according to that idea, what you're seeing is mostly water, but much less so what you're vaping. You might see if you can find anything more scientific on that.
E-liquid contains very little water, plus around 1 drop (.02-.05 ml) is vaporized per hit, how much steam would 5% of that make?