Minecraft wiki entry for Placed_feature, associated text: random_offset—Applies an offset to the current position. Note that the even though X and Z share the same int provider, they are individually sampled, so a different offset can be applied to X and Z.
 xz_spread: Int provider between -16 and 16.
Int provider[show]
 y_spread: Int provider between -16 and 16.
Int provider[show]