It's probably time or mileage computed. My '20 Traverse has that feature also and it's been at 85% for a while also. It doesn't get driven much so I don't know what it's doing currently. 10k miles on it currently.
In my experience an air filter lasts 50,000 miles or more unless you drive on dusty dirt roads. My 06 Malibu went 72,000 miles on one air filter and I didn't notice any difference when I changed it. A dirty air filter filters better until it becomes overly restrictive.