I don't know what you did to your population because a million is 10^6, hence
When you round off to 3 sf, you keep only the first 3 digits from the left. Here are examples:
36841 to 3sf becomes : 36800
514.52 to 3 sf becomes : 515
0.01655 to 3 sf becomes : 0.0166
If you have a digit less than 5 to the right of the last number you are taking in the rounded figure, you round down. If the digit is instead equal to 5 or is larger than 5, you round up.
Can you work out the solution to your problem now?