To me the probability of the previous owner adding incorrect volume of oil seems greater than the probability that a 2017 with 500 miles can make 3/4 of a liter of oil disappear without obvious signs of burning or leakage.
I believe mysterious & serious oil consumption is a rarity, even on a 500 mile bike.
If you did not personally note a correct oil level prior to your rides you unfortunately do not have a valid initial data point to draw any conclusions from yet.
I would recommend collecting some fresh data; note current oil level and the method/ angle/location that you used to measure. Then ride a lot more and periodically note any changes in oil lever using same method, angle of the bike, and location where it is parked and measured. It does make a difference with these tiny sump engines.
I believe the results might just indicate an inadequate initial oil level at time of purchase.