So this is probably not the right place to post this, but I figured since we gather seeds and all, someone might be able to help me out. I've been doing a lot of reading up and I think I understand gardening for the most part, but what I don't understand is the crossbreeding spreadhseet that is going around, like this one.

From what I understand, only TWO plants are needed in order to crossbreed and produce seeds on top of product. This spreadsheet lists Plant 1 (Harvested), Plant 2 (Adjacent), and Plant 3 (Adjacent). To me, this sounds like three plants are needed in order to crossbreed and produce seeds -- the two adjacent listed and the one harvested in the middle. So what's the deal here? Thanks in advance!