Step 1: Understand the concept of 流量 (flow) and 存量 (stock)
流量 (flow) refers to the quantity of something that changes or moves over a specific period of time, while 存量 (stock) refers to the quantity of something at a particular point in time.

Step 2: Analyze the given statement about 外汇储备量 (foreign exchange reserves) on a specific date
The statement mentions 2003年十二月31日的外汇储备量, which translates to the foreign exchange reserves on December 31, 2003、This refers to the amount of foreign exchange reserves at a specific point in time.

Step 3: Determine whether the given statement represents 流量 (flow) or 存量 (stock)
Since the statement refers to the amount of foreign exchange reserves on December 31, 2003, it is describing the quantity at a particular point in time, not over a period.

Step 4: Conclude whether the statement is describing 流量 or 存量
Given that it describes the quantity at a specific point in time, it represents 存量 (stock).

The final answer is: $\boxed{错误}$