Crop Adjust is a system in which users are able to earn bonus crops on top of their normal amounts from breaking crops. This will result in getting 1 additional crop per hit. These are typically given out as either Crate rewards, or as rewards for completing specific quests depending on the gamemode.
A user is able to check which Crop Bonuses they have unlocked by doing /cropadjust and viewing the GUI.
The "Bonus" Calculation works like this: When you break the Crop, it will take whatever amount you were supposed to get, and would add 1 additional to the Item Stack. Because of this, it is sometimes hard to spot on Crops that are effected by the Fortune enchantment, due to those crops giving different amounts on every hit. If you are using Auto Replant, it will also take one crop to replant as well, which happens regardless of application of the bonus.