The Chinese language is full of subtleties. There are hundreds of dialects throughout the country and the inhabitants of a region often find that their neighbors speak a foreign language.
This is an additional difficulty for any laowai (litt. « foreigner ») who is already having a hard time learning Mandarin. Although Mandarin is the official language, not everyone speaks it, and sometimes you may have to find another way to communicate.
Despite these linguistic differences, the Chinese have a common way of communicating numbers. These are gestures performed with one hand, which refer to the corresponding characters. This method was also designed to avoid confusion between similar sounds (eg between 4 which pronounces « si » and 10 which pronounces « shi »). This is why it is also used even between Chinese people who speak the same dialect but want to avoid any kind of confusion.