Keep in mind that the brigades with J-20s mix them with J-16s and J-10Cs as well. 16 is probably the upper-end estimate.
Does 9th brigade operate J-10Cs?
I was under the impression that it operated Su-30MKKs prior to making the shift to J-20s.
Considering from 9th brigade late last year the highest serial from 9th brigade was 62009, (i.e.: 9 J-20s likely in service), the idea that there are 16 J-20s at Wuhu is sensibly around what we expect.
So my running tally for in service J-20s:
Wuhu, 9th Brigade: at least 9 J-20s in service, possibly at least 16 J-20s in service based on the above "2 dadui" post
Cangzhou: at least 4 J-20s in service, each serial confirmed
Dingxin: at least 8 J-20s in service, each serial confirmed
Which gives us at least 28 J-20s service, which if we take the the traditional "1:3/1:2 ratio" of "confirmed to actual" aircraft in service will give us an estimate of somewhere around 50-60 J-20s in service.