We've known for a long time now that their "robotaxi" fleet in Austin is about 30-50 vehicles. It started off much lower and has grown to about 50 today. There's actually a community project to track individual vehicles that has more exact figures.

Currently it's at 58 unique vehicles (based on license plates) with about 22 that haven't been seen in over a month

https://robotaxitracker.com/