We are talking about an IM right? Intramuscular injection? So I'm looking at the Modena guidelines from CDC - it's an IM injection as in injected in to the deltoid muscle, of 0.5ml taken twice three weeks apart. The amount that needs to be drawn up is exactly 0.5ml per shot.

https://www.cdc.gov/vaccines/covid-19/info-by-product/moderna/downloads/prep-and-admin-summary.pdf

You don't asperate small shot like that, because it then becomes 0.3 ml or less, for the tiny amount to be injected in terms of a shot. The Intramuscular area is the deltoid it's a muscle not a vein. Wasn't he a sports coach or a WWE wrestler? He'd know a deltoid right? Sorry. Injections are similar to Sub Cutaneous or under the skin shots such as Cephalexin, or insulin... for exact shot amounts such as injections and vaccinations and exact amounts you are aiming for 0.5ml as the amount of DNA fragments to be introduced to the immune system.

For IV line insertions and single boluses to the line you aspirate and of course watch the IV lines, for the dreaded air bubbles but that's not an injection.