here's an example number
9.012345
here, 0 is the tenths place (it can be represented as a number /10)
1 is the hundredths place (number/100)
2 is the thousandths place (number/1000) and so on....
if i were to round this number to the nearest thousandth, i look at the fourth decimal point. since it is less than 5, the above number rounded to the nearest thousandth is...
9.012
now do this for your number