Coming back to: Reconstitution volumes that produce round numbers, tabulated

On the subject in the title: Reconstitution volumes that produce round numbers, tabulated Working notes rather than a conclusion.

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

I have a 15 mg vial of tirzepatide and I am working to a 0.25 mg step. My syringes are U-100 insulin syringes, 1.0 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.

Why "add 2 mL" is not an instruction: the powder in the vial takes up space. "Add 2 mL to a 10 mL vial" and "add 2 mL of diluent so the final volume is approximately 2 mL" are different instructions. Stating the final target volume is clearer than stating the diluent added.

post #2 answers the question as asked. The question underneath it is different.

For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use.