When Nai Nai explains why the nanny stole Billi's egg, she mentioned that the food rationing was imposed when Billi was little. China's food rationing period ended in the early 1980s in the northern provinces, considering the film was set in 2019 and Billi left China 20 or so years ago, it was highly unlikely she experienced food rationing in the year 1999 when food and consumer goods were already widely available.
1:22:14 As Billi runs down the street, the crew van with its door open is reflected in the last billboard.