holdover

Something left behind, saved or remaining from an earlier time.

That policy is a holdover from days of punch card data entry.

Castle Rock Middle School was a frowning pile of red brick standing between the Post Office and the Library, a holdover from the time when the town elders didn't feel entirely comfortable with a school unless it looked like a reformatory.

The distance (at target) by which a rifle scope is aimed higher than the intended point of impact in order to compensate for bullet drop over the distance to the target.

This rangefinder not only measures the distance to the target, but also provides a digital readout of the inches of holdover at that distance.