Yeah there are a total of 10 Inquisitors who have been revealed so far:
-Grand Inquisitor
-Second Sister
-Fifth Brother
-Sixth Brother
-Seventh Sister
-Eighth Brother
-Ninth Sister
-Tenth Brother
Along with these two unidentified Inquisitors:
https://i.imgur.com/8ZYAyhs.jpg
So unless Kylo actually uses his superior Force power here, he gets stomped.
The "Fourth Sister" who appeared in Return to Vader's Castle was actually just a Rebel imposter:
https://i.imgur.com/zL2rczo.jpg
https://i.imgur.com/UMg6sVr.jpg
I'm sure there was a third and fourth Inquisitor -- we just haven't actually seen them yet.