Notice that a 5 mg vial in 2 mL and a 10 mg vial in 4 mL both give 2.5 mg/mL and behave identically at the syringe. Concentration, not vial size, is what the syringe marks answer to. I run the division and the unit conversion through the Peptide Tracker & Calculator rather than doing it in my head at 7 am, because the failure mode is a silent factor-of-ten error, not an obviously wrong number.