AHH shit. I think some eliquid manufacturers often fuck up with shortfaills and bottles you add nicotine to yourself because they don't bother taking into account the amount of nicotine you add manually so they don't know how much you're going to dilute the flavour with the nic shots, that would mean the smaller 10ml bottles have the intended flavour though, the flavour the manufacturer initially intended when they made the recipe, not the opposite.
Some reputable retailers, like manabush recommend that instead of adding nic shots to the big bottles you get 10 ml of the flavoured juice at 18mg and add that to the short fills so the big bottles keep the intended flavour.
It's not something most people worry about though, you're only diluting it a little so most people are happy.