In the days when you used custom printed forms that had a number printed on them by the printer - when you loaded a new box of paper into your printer you had to input the first form number into the system so they'd match.

If you opened boxes in "whatever" order you'd have invoice numbers that would run contiguous for 150 or so counts (the number of forms in the box), then skip to the next multiple of 150 to correspond to when the next (or previous!) box had been used.