Board Thread:Help Desk - Hay Day Wiki/@comment-26479907-20150609123259/@comment-5965519-20150617235827

Yes NR89 - Barnswallow has explained it well. In another thread  we had this discussion and I tried explaining it like this, in case a different explanation offers further illumination:

" I think the way to understand this is to think of it like "what amount of this crop is new to my silo, that I am now adding in?"

Everytime you plant one field, or plot, with one crop - you are taking it OUT of your silo to plant. That plot then yields 2 of that crop - it gives you one back, replenishing the store that you used to plant it, and then gives you 1 new one. So it is giving you one new unit of that crop to add to your existing store in your silo, while simply replenishing the one that you used to generate that harvest.

The derby recognizes the one that is the new addition only, not the replenished seedstock you used to plant.