Both milliliters (ml) and ounces (oz) are units used to measure the volume of fluid. One ounce is about 29.6 milliliters. If we multiply this by 16, we'll get about 473ml, which doesn't fit Sarah's original measurements. 473ml is obviously way less than 630ml. Her calculation would be correct if she wrote down 21.3oz (630ml ÷ 29.6 = 21.3oz).
