Anyway, I'm not trying to discourage people from buying new fun electronics to support their hobby. Just giving an alternative above since you are probably only going to do a handful of capacity tests in your life unless you're running a YouTube channel or a battery/electronics company.
Here's a $0 method that might work well enough. It's going to be less accurate than a good shunt but maybe more accurate than a cheapo shunt:
1) find something which draws ~9A from your battery, according to your BMS (a couple light bulbs connected to the inverter output)
2) use the 10A mode of your cheap multimeter and install it in-line with the battery, just like you would that $18 board from Alibaba
3) measure 0A and 9A load, and fit a line to the multimeter-vs-BMS current readings. This gives you offset and gain correction.
4) remove the multimeter and thereafter just rely on the BMS's reading but correct it using the values calculated in the last step
To reduce the risk of step (2) blowing your multimeter fuse, you can apply a short wire across the ammeter leads until the current has stabilized for your measurement, then remove it.
As a bonus, now you can rely on your BMS's current readings for the lifetime of your battery, in all likelihood. Most of the error is in the shunt resistance variation which is fixed after manufacturing, not random voltage offset of the electronics, if they've chosen a low-offset analog front end in the BMS design.
Two types of shunts, two methods of "calibration".
If you have a higher capacity shunt, notice that it seemingly has a notch cut out of one of the bars? That is the calibration, totally automated process, sends a current, measures how much out of tolerance, and adjusts the notch size accordingly.
Smaller shunts (like the $18 one) look like a half loop. Since the measurement circuit is built in (voltage measurement), the resistance of the shunt is once again measured by sending a current through the shunt, and an offset value is stored in non-volatile memory.
Nearly every component in any device is manufactured, measured, and or calibrated to one extent or another. Every manufacturing facility I have worked in, has their own calibration facility or team.
Some items measured in costs by fractions of a cent (for example resistors) have broader tolerances, and of course you pay more for tighter tolerances.
I'm not sure why you would think shunts are somehow special and just shipped hoping the customer won't notice. I can tell you that the 3 different (under $50) models of cell testers I have tried, all agree within a tenth of an amp hour with two different (complete with actual lab calibration certificates) models of lab equipment that I own.
I am sure there are vendors out there that sale terribly uncalibrated equipment, but they have a tendency to go out of business.
Daly seems to have their own method of business, and it will either adapt to meet the demands of the market, or wind up as a "remember this company" type of company. They do have a calibration method that they apparently don't want average users to perform. I have no clue why they don't do a better job in the factory, but it is hurting their business and reputation in a very competitive field.