Impressive. But off the top of my head I can count a few more than 10 YC companies valued at $1B or more:
1) Airbnb
2) Quora
3) Stripe
4) Dropbox
5) Instacart
6) Coinbase
7) Reddit
8) Cruise
9) Twitch
10) Gusto
11) Zenefits
12) Docker
13) Machine Zone
And a few more that are pretty close to $1B