Why is there a slash on the American visa number 0?

There is a slash on the American visa number 0, which is a Greek letter. A successful visa can be valid for five years. The validity of the visa does not represent the time spent in the United States. A visa is only a document to enter the United States. The legal residence period is determined by the US Immigration Service. When entering the country, the immigration officer will endorse the legal residence period on the form, which is the most important thing. The visa number of an American visa needs to be provided at the time of renewal, and the last visa number will be required at the time of renewal.