It's not bad tbh, keep eye on topups & watch exhaust for burning oil so to speak, but 500ml in 5 months seems ok, I used to top-up 1 litre every think was 1000 miles in my old S4 V8, I do recall it being thirsty.
Also 40tdi (2.0) - I have an oil change every 15k. I have not needed to top up between oil changes. At 76k km now.
That being said, give it a few oil changes first. I've heard some people have to top up in early km of the car
Unless the car is using more than 1l per 1000m then Audi do not see that as excessive oil consumption. Biggest issue for the C8 is the lack of a physical dip stick so it is hard to tell if the il really needs topping up or if the car is just in nanny mode, likewise it is hard to be sure that the oil has been filled to the correct level.
I was very surprised on Sunday when oil warning light and engine man lights came on 10 week old Q5 40TDI with 2200 miles.
Audi assist came -reset software for engine mgmt and said needed oil- I asked why at only 2200 miles - technician said will use a lot of oil till 5k miles then should be ok between services
Not used to this after 5 Land Rover's and a Mercedes - not impressed.