I have one and it tracks very poorly. It tracks only the usage time regardless of how fast the fan is running.

When on auto, it is mostly spinning at idle, hardly sucking air through the filter, and as such it's hardly contaminating the air filter (in fact the airflow is so low I stopped using auto mode at all, there is just no point).

It also doesn't take into account how contaiminated the ambient air is (even though it has an air quality sensor on the one I have).

I run mine at about 40% so I use the filters about 2-3 lifetimes :) Even that is a pessimistic approach IMO because the air here is very clean. I mainly have it because of hayfever (pollen allergy).