The values
- Japanese sets: 6,959
- English sets: 9,110
Where it comes from
The line in the source
As of September 2017, collectively, there are 6,959 cards in Japanese sets and 9,110 cards in English sets.
In English
Wikipedia "List of Pokémon Trading Card Game sets" intro; no inline citation for this sentence (footnote [2] after the 23.6bn sentence points to the TPC corporate page, which does not carry it). Treat as C: a community-compiled stock figure, English cards 1.31x Japanese.