It's not exactly a gigantic number compared to conventional delivery companies. FedEx was shipping over 15 million packages per day as of February, while Domino's Pizza sends more than 2 million pizzas per day. Starship is a rounding error by comparison, although it's also serving a far smaller number of locations that only recently included college and university campuses in the US.
The figure is notable all the same. It shows that there is a market for delivery robots, however modest, and that it's not just an experiment. We'd add that many companies are just starting robotic deliveries -- you're likely to see a surge in these figures across the industry.