How do you evaluate #e^(-3.4)# using a calculator to four decimal places?
Since you need 4 decimal places, you need to look at the 5th decimal place. If it's 5 or more, you add 1 to the 4th decimal place. If it's less than 5, you leave the 4th decimal as it is.
In this case, the 5th decimal place is 7 and the 4th is 3. Since 7>5, the 4th decimal place changes from 3 to 4.