Combined Distance From Center (CDFC)
The bullet's path takes it above and below the line of sight as it travels down range, and cross winds blow it off course, especially at longer ranges. At any given range, the offsets due to path and wind combine to move the bullet further away from the bull's-eye than either offset could cause alone. In most cases, the direction from the center of the target to where the bullet strikes is not important, but the distance is. This distance is the combined distance from center (CDFC).