I actually work (occasionally) at a vaccine clinic, and have been trained in drawing up medications for all sorts of reasons. It makes no sense at all that they would draw up 6 doses into one syringe, and then try to redistribute those doses into other syringes. That’s not how you are supposed to do it.
This person failed basic nursing medication handling, safety and dispensing.
Before giving any medication, you check the dose. The dose for Pfizer/BioNtech is 0.3ml. The dose for Moderna is 0.5ml. (I have not given Jannsen or AZ, but the doses for those are 0.5ml as well per a quick google. I have no idea on Sputnik, as the chances of me giving that vaccine asymptotically approach zero).
The syringes used are generally, but not always, 1cc total. Sometimes 3cc. You should notice the difference between 0.5cc and 3cc in a 3cc syringe - - a little bit in the syringe versus the whole syringe. This is beyond a reasonable mistake.