> but this year the amount of money transacted through UPI crossed 1 billion USD for the first time

You're off by a few zeroes. UPI transactions totalled 1 trillion USD last year. Figures from last month can be seen on their website - nearly $135 billion for September 2022.[1]

[1]: https://www.npci.org.in/what-we-do/upi/upi-ecosystem-statist...