What it shows
Kitchen shows what has been ordered and what stage it is at. Orders arrive as the floor confirms them, so cooking starts without anyone carrying a docket.
Mark items done as they go out
Not in a batch at the end of service. The screen's value is that it is current — a kitchen that updates it afterwards has a record, not a tool.
When it is current, the floor can see progress without walking in to ask, which is the thing it actually saves.
If the screen is cluttered with old orders
Items are not being marked done as they go out. The screen reflects exactly what the kitchen tells it, and nothing else.
If an order never appeared
It was not confirmed on the POS. An order being built is not sent to the kitchen until the floor confirms it.
Why this feeds everything else
An order marked complete is what closes the loop on the table, the delivery and the stock depletion through recipes. A kitchen screen kept current is not administration — it is what makes the rest of the numbers true.
During a rush
The discipline that holds up under pressure is the simple one: confirm orders on the floor, mark them done in the kitchen. Everything else can be tidied afterwards; those two cannot.
The service chapter of the RestaurantOS manual covers the full flow.