What the punch marks
What a clock records, what everyone assumes it records, and the distance between them.
What the Punch Actually Marks
A clock records the moment somebody touched it. Everything downstream treats that as the start of work, and the two are separated by unowned minutes.
Nineteen Minutes
The unpaid edge of a shift is small enough that nobody raises it and large enough that it is the biggest number in the subject. The arithmetic is the whole argument.
Required, Expected, or Just Sensible
Whether an activity around the edge of a shift is paid turns on who demanded it. The three categories look identical from outside and are decided very differently.
Too Small to Count
Every system ignores small amounts of time, and it has to. The question is what makes an amount small, and the usual answer gets it the wrong way round.
Writing Down Where the Day Starts
One page per site, listing what happens at the edge and whether it is inside the paid day. Producing it is where the decisions actually get made.
Two Clocks That Never Speak
The building records when people arrive and the payroll system records when they clocked on. Both exist, both have the same names on them, and nothing joins them.
What a Punch Does Not Establish
Six things the clock record is routinely used to prove and cannot. Naming them protects the record everywhere it is sound.