The foreign exchange quotation of each bank is different. This is an over-the-counter (OTC) market, not a unified place like an exchange, so each bank's quotation is different (depending on their respective positions and views on the market, etc.). The central bank has a benchmark exchange rate, and commercial banks float a certain exchange rate accordingly. However, because this is a highly liquid market, the quotations of major banks are very different. The specific exchange rate quotation can refer to the foreign exchange quotation of the bank where your business is located, which is generally refreshed every 20 seconds.