Why "add 2 mL" is not an instruction

The question in the title: Why "add 2 mL" is not an instruction I will give what I have already checked below so nobody repeats it.

Practical question with the units stated, because I have seen how quickly these go wrong without them.

I have a 10 mg vial of semaglutide and I am working to a 2.5 mg step. My syringes are U-100 insulin syringes, 0.5 mL barrel.

I can do the arithmetic and I have done it twice, getting the same answer both times, but I would like someone to check the reasoning rather than the number — specifically whether I have thought about the residual volume correctly, and whether the graduation I am landing on is one a person can actually read.

Picking up post #3: that is the part I would want checked first.

Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.

That is a cleaner way of putting what I was circling around.

Do not shake. Swirl, or leave it. Vigorous agitation introduces air and shear, and neither helps a peptide go into solution any faster than patience does.

Confirming post #23 from a second method, which matters more than confirming it from a second person.

Do not shake. Swirl, or leave it. Vigorous agitation introduces air and shear, and neither helps a peptide go into solution any faster than patience does.

On reflection I would soften that slightly.