AccuBattery should detect the design capacity of the battery during the initial setup. The only time you'd want to change it is if you have a phone with a user replaceable battery and you swapped in a larger capacity battery.
To JakobM, it's common to see brand new Li-ion batteries with lower than rated capacities. I've personally never had one right at 100% out of the box, and have always stuck with flagships from major manufacturer. From
https://batteryuniversity.com/index.php/learn/article/how_to_prolong_lithium_based_batteries
In one of their test of 11 batteries, they all had initial capacities of 88-94%, putting yours at the high end of average. The phone may have initially had an even higher capacity, but naturally degraded a bit while sitting on the shelf for months. Yours was released last August. I'm currently using an LG V60 released only a month ago, and it was about 94% of rated capacity from the start.
I have the paid version and there's no auto detect for the factory bat spec. Maybe so on some devices but certainly not this one, Note 10 plus running on Pie.
After over 6 months it's best guess is 98% of its original capacity. It's gotten some heat and full charges but I've been conservative with it's charge cycles 90% of its life.
It estimates capacity by total rated capacity and how many watts of power it takes to reach a particular voltage level ie mah.
If you do a full charge this rating will change and reflect a number closer to its true capacity.
Seems fairly accurate if set up correctly.
I think it's a great battery conservation tool if use it correctly and limit charges to 70%
It also has the battery temp displayed. Not sure if it factors that in or not. Read all the literature on it.
When charging, temps become a big issue as you approach the battery's full charge V+.
Temperature causes less damage at lesser voltages. The damage happens even when store an LI cell but active high current drains accelerate it.
The device's high shutdown temp for charging is way too high. Need to keep charging temps below 90F as much as possible; 72 is better but hard to do.
They top charge can always limited though... by you.
I put a damp rage on it when charging every time which drives the device temp to 10-20F more than it would see without it. The fuller the top charge, the hotter it gets especially in high ambient temps...
Takes about 20 minutes for a short charge with fast charging vs a much more damaging 56+ minutes for a full charge from the 30-40% discharge range.
The app also has an adjustable charge target to audible tell when it's reached. Works perfectly.
So... time will tell.