In that case, so far there are around 3 dadui of J-20 with WS-10C confirmed. The 3rd dadui at 1st brigade still operate J-11 and the 5th brigade is unlikely to have more than 1 dadui.
That gives a total of 3 x 12 = 36 planes. Assuming it was produced over 2 years (2020 and 2021) that averages out to 18 planes per year. It is unclear when the other J-20 at 9th brigade was made and when exactly J-20 with WS-10C start serial production. It could have started earlier with a lower rate while the none WS-10C J-20 product is getting warped up so those factors cancel each other out and 2 years would still be a good estimate.
We will have to wait and see if the production numbers ramp up.
CB0256 represents the highest estimate for total J-20 airframes based on the CBAXYZ system.
The earliest that we started seeing serial production J-20s with WS-10s was mid-late 2019.
Counting serial numbers at given units is a useful way for establishing a floor estimate that is likely at least a few months out of date.