Dealerships stamp and signature the counter slip of payorder. PBO is issued after the payment is credited. The PBO is issued 4-5 days after.
It's a loophole that allows dealerships to delay the booking by a week or 2 if they have used up their current quota and would get more next month or they want to book investor vehicles first.
Better keep calling the sales person about PBO so they are annoyed enough to book your vehicle as soon as possible. Preferably twice a day.