For milk.
The driver shows up and measures how much milk is in the tank with a dip stick.
He then turns on a mixer that mixes the milk and takes a couple of samples.
He then loads the milk in his trailer mixing it with everyone else's milk.
When he gets to the drop off point they test every sample for bacteria.
If all samples pass he is allowed to unload.
If one sample fails he is not allowed to unload and the farm that bad sample came from just bought that entire load.
From these samples they also test what each farm shipped as to quality of the milk.
Fluid milk is bought and sold with a butter fat of 3.5% So if your milk is 3.8% you get a premium for it.
Here is a typical milk check.
A threw E tells how much the farmer shipped
It shows total pounds shipped and what the milk contains for butterfat and protein.
This farmer shipped 113,448 lbs of milk in this month.
It had 4311 lbs of butterfat that computes to 3.80%
So while farm A and Farm B may both ship 100,000lbs per month farm A may get a bigger check because his milk is higher butter fat. In other words farm A really shipped more milk because when they water the milk down to get the desired 3.5% butterfat he was allowed to add more water so he had more milk.
F and I is just adjustment to location so the milk is produced around the country.
G is a volume premium if you ship large amounts such a full truck loads.
H is your Cell Count.
J is your hauling fee; milk promotion fee for commercials or bill boards; and your coop fees.
I do not know grain prices well enough to comment so maybe one of these other guys can explain.
But the way I understand it is the price you see on the exchange is delivered to mouth of the Mississippi.
So while corn may be listed a $3.60 per bushel there are many deduction taken out of that price to cover shipping; drying; and other things to get it to a base level.