You friend doesn’t understand lot numbers.
The numbers are not unique to the individual dose administered. If they were, the vials would have to be unique and could only contain a single dose which is obviously not true.
The number of doses in a lot may vary considerably.
There has been some controversy that different lots are more dangerous than others because the number of adverse reactions vary between lots but this purely a function of the size of the lots.
I haven’t been able to locate information typical lot sizes but I can assure (I used to manage quality control for a major program) that they lots are not specific to an individual.
thank you for proving you’re a major player in drug pushing...