Pull Back on Syringe?

Not sure this is the right forum, but I have a question about meds given via syringe...hope somebody can help!

OK, so disclaimer...I'm a student learning about Med Pass, and this is a bit detailed because I want to be sure I explain the exact part of the process I am confused about! So bare with me...LOL!

Today we were going over drawing up the med from the vial/bottle into a syringe. We were show how to pull back on the plunger to draw in the amount (let's say 30mL) of air, then pierce the lid of the vial and "inject" the air into the vial to displace the medication and to maintain the pressure. OK - I get that bit....

Now, turn the vial/bottle upside down and draw up the liquid into the syringe to the amount needed (30mL in my example). Slide the needle out of the vial. OK - got all that...

Now, my tutor explained that there is a small amount of med left in the shaft of the needle, so we need to draw back further to create a bubble of air in the body of the syringe, then push on the plunger again to push that air bubble out and observe a tiny amount of he liquid appear at the tip of the needle. OK - now you've lost me!! Why bother with this step - surely if there is medication in the shaft after the initial draw, and then I pull back, then push back up until I see the dot at the tip of the needle, I am just back to square-one, because to get the dot of med at the tip of the needle, it has to pass up the shaft to get there, so now I *still* have medication in the shaft...I don't get it!

I did ask her to explain but after going over it twice I felt embarrassed asking her a third time! Can anyone help...why is this step even necessary. It seems to me to be introducing a risk of having air bubbles in the med more than helping!

Thank so much in advance!