Noob Question about Dosing

Hey guys, I have a question concerning dosing. I dont really understand how these numbers work. I’m going to be starting my third cycle soon, (Primo, deca, enanthate) and a friend of mine told me to dose them like this:
1-12 Test E - 600mg/week (2cc/week)
1-12 Deca - 500mg/week (2cc/week)
1-12 Primo - 400mg/week (4cc/week)

Now I dont understand what any of this means. When I go to the pharmacy and tell the nurse to give me the injection I tell him either 1/2 cm or 1 cm so what exactly am I going to be taking. I know its a weird question…

Where are you from?

Here is how this works:
1 cc = 1 ml
Test250 for example is 250mg per 1 ml/cc

what? The nurses don’t work by volume, they work by how many cm down the syringe they go? This is all very weird.

I can’t understand why anyone would want to be injected by someone else