What to buy
The linear-foot estimate is the more robust purchasing number when you can choose among stock lengths. The “stock pieces” result simply divides that waste-adjusted footage by the selected length and rounds up; it does not generate a splice layout.
Board gap matters
Actual board width plus the intended gap determines how many rows cover the deck. Wet pressure-treated boards may change dimension as they dry, so follow the decking manufacturer’s installation guidance rather than assuming one universal gap.