i'd say thats just a tiny bit below average if you use it pretty frequently daily. 80% is when apple replace batteries (if within warranty), and that's with around 2 years of use. as a rough rule of thumb i'd expect your battery health to be at 90% after 1year so you're not that far off.

Just got the xs max though Mob, anyone after or debating getting a new iPhone I would highly recommend going through him, got it me for less then retail and he is was very helpful with all the questions I asked him, was even sent via special Saturday delivery aswell which was great