To perform the calculations for the circumference and area of a circle, you may have used the π key on your calculator. When you press this key, the screen of your calculator shows more digits than the 3.14 you use as an approximation for pi.
Depending on the type of calculator you have, you may see the first eight digits of pi, or you may see more than that. No matter how many digits you see, your calculator is still giving you an approximation for π.