OK, I'll *try* to explain how I *think* these triggers work, in layman's terms as requested. SettlementBuildingFinished returns the name of the building just built. If that name is not part of the hinterland_farms build tree, a value of zero assigned to whatever temp variable is being used. If the name is part of the hinterland_farms build tree, the temp variable is assigned the number corresponding to that level farm. This number is then compared to the number corresponding to the building name on the other side of the arguement, namely farms (=1). The building name on the other side is also what specifies which build tree to use for the evaluation.
So, if you build a port, SBF = 0 and farms = 1, so the trigger goes to false and nothing happens. If you build a farm, 1=1 and you get a point for good farmer. For farms+1, 2>1 and you get another point. So maxing the farms in a settlement should give you 5 points. Why is the threshold 6? I have no clue. Chalk it up to piss poor playtesting, not that there's any OTHER evidence of that.