Let's say you draw oil from a vial. You want to draw 1CC. You draw until the oil reach the 1cc mark. But if you remove the needle, there is always a little bit of oil remaining in the bottom part. About 0,15ml. Do you need to ''calculate your drawing'' so that once the needle is removed the total amount of oil reach the 1cc mark or you draw until your reach the 1cc mark, draw a little more to remove the remaining oil from the seringue part then switch needle (So basically, with the needle remove, the oil will reach the 1,15 CC mark)
I know it's confusing but it's really bothering me!