When the hens are "punching the time clock", the clock advances one minute per "punch" though the line of workers is moving much quicker than that.
When Porky goes to stop the assembly line, the boxes on the conveyor belt disappear at the point where Porky was picking them up before.
As the chickens are clocking in, the arrangement of the time cards in the 'Out' slots do not change, indicating it is just background.