You are reading far too much into "capacity."
Capacity, or "health," is:
a) non-linear, and
b) inexact.
It is defined as current capacity (a real value for your battery), divided by design capacity. Design capacity is an estimated average value across all batteries of that model.
The vagaries of battery manufacture mean that initial actual capacities of individual batteries vary around an estimated average or target value. All manufactured items have a target value tempered by an allowable tolerance (±). Otherwise, very little could be shipped, and a notebook computer with a "no-tolerance" battery would be unaffordable even for Tim Cook. Allowable tolerances in device design keeps affordable products available to you.
My last Macbook Pro had 102% capacity when new. That means someone else's must have started at 98%. Now after 11 years of use mine still is doing OK with about 84% "health," condition reporting as "normal," and it still gives acceptable runtime on battery.
As for non-linear, the data backing that truth is in this partial history of my Macbook Pro battery health:
Note that between 5 May 2022 and 25 Jun 2022, capacity plummeted by almost 10 points. By 12 Aug it was back to 82%. When I looked three days ago, it was showing 84%. Are you going to lose sleep over something so inexact??
PLEASE do not obsess over such an inexact and non-linear value. As far as I can tell, Health exists not for our use but for Apple service techs. The traditional Apple policy on WARRANTY replacement of batteries is that, if a battery falls below 80 % capacity at less than 1000 cycles on a computer STILL COVERED BY WARRANTY, Apple may elect to replace the battery at no charge to the owner. That's it.
Use your computer, enjoy your computer. There are far more things in this old world to fret over than a silly, inexact metric useful only for service techs' reference.
