TITLE: Is 4 the second or third digit of pi
QUESTION [8 upvotes]: If someone says that they know 10 digits of pi, does that mean that they know ten digits starting with the 3 in 3.14 or with the 1 in 3.14?

REPLY [24 votes]: People generally specify digits after the decimal place to say how many digits of pi they know.
Fun fact: if you know pi to 39 digits, you have the accuracy to approximate any circle around the observable universe to the width of a proton: going farther is not practical.