The waste of time and energy is unfortunately ours trying to fathom out what people mean when they speak such nonsense. The only way ‘get’ can be used in this circumstance is ‘can you get (whatever) for me’, ‘can I get’ means you are asking if you can go behind the counter, reach up on the shelf and get it. The server should say, ‘Yep, it’s over there, go and get it’