When it comes to hundreds and thousands and even millions, you can tell how much bigger something is by how many more zeros are at the end. Each new zero added, is another rank up. The system goes:
so on and so forth. There are 2 zeros in 700, and only 1 zero in 70, the difference in zeros is 1, so you can refer to the chart and conclude that 700 is 10 times bigger than 70. You could also divide 700 by 70 to get 10. This is more accurate, but the chart is simpler.