Because the total amount of money ÷ the number of subscriptions for primary school students' mathematics newspapers = the amount of money for a primary school students' mathematics newspaper (certain),

That is to say, the proportion between the total amount of money and the number of subscriptions of primary school mathematics newspapers is certain, which is in direct proportion.

Therefore, the number of copies subscribed to the primary school mathematics newspaper is directly proportional to the total amount of money.

So the answer is: correct.