How do I find if my macbook air's remaining battery capacity is less than 80%. When I go system preferences/battery/battery health, it just says it's normal. I want to avoid if possible the trek to the Apple Centre to have it checked.

How do I find if my macbook air's remaining battery capacity is less than 80%. When I go system preferences/battery/battery health, it just says it's normal. I want to avoid if possible the trek to the Apple Centre to have it checked. I've asked this question before and was told that I had to go to the store to find out - however on the web it said I should have the maximum capacity on my battery heath window - https://osxdaily.com/2021/07/13/how-check-mac-battery-health/ (as I said before it doesn't have that on mine.)