Zeroing

Zeroing refers to calibrating a weapon scope so that the crosshairs meet the expected point of impact of the weapon's projectile at a specific distance. When aiming at a target the same distance away, zero adjustment from the crosshairs is needed.

Battlefield 4
Battlefield 4 allows certain weapons (currently bolt-action rifles) to be zeroed, allowing the shooter to more reliably hit targets at a distance and to maintain more view of the ground. A set of predetermined ranges is chosen by pressing while "aiming down sight".

Whether this is a function of the Recon kit, the weapon, and/or the scope will be revealed in the future.