When you round a number to the nearest hundred, its number before last number, remains the same if the last number is 5 or lower. Instead of that, if last number is greater than 5, then, number before last number changes to the next interger.
In this case,700 has been rounded to the nearest hundred. Then, the aactual number (actual distance) can be between the following interval:
696 ≤ 700 ≤ 705
In fact, if you round 696 the answer is 700, if you round 705, the answer again is 700.