I see 2 hundredths of a gram between drops of pg and vg. and it can be more between using different spouts, eye droppers, and dropper bottles, there is a good variance between them all. - and it's a repeatable accuracy.
Just Curious:
Did you see a Difference in Variance between the PG and the VG. In that, it is Easier to "Over Drop" a Thick Liquid than a Thinner Liquid.
And there is No Such Thing as an "Under Dropping". Because the Drop Will Not Fall.