It's expected that especially over the first year you will have between 4% and 10% battery degredation. Apparently after that it slows down considerably. I have seen reports of some Model 3's that after 100K are still somewhere around the 10% ish battery degradation mark. There are plenty of reports also that indicate that in the winter time, this number will show lower, probably just due to the BMS and how much capacity it believes is in the battery. In summary don't worry about it....I spent too much time worrying about this on my Model 3.