With a dose order of 10mg and the stock bottle being labeled 30mg/mL, the nurse will need to draw up .33mL. We come to this answer by taking the dose order of 10mg and multiplying by the stock bottle amount of 1mL/30mg. The 30mg/mL was inverted to account for units so that mg cancels out and we are left with mL answer.
Total mL needed = 10mg * (1mL/30mg) = .33mL