Pistons specs question for 340 build

Anything above the crown is +cc, anything under it is -cc. Think of it like a flat top box and use that to determine what the calculator is asking. Is it combustion chamber volume at TDC, cause a dome is gonna give you a smaller chamber volume and higher CR. A TRW forged 340 is gonna have some extra dome on top, +cc. A cast Dodge 360 is gonna have a dish, -cc. even a flat top with valve reliefs is gonna be a small - number just like a dish. We can beat this sideways but ultimately its what the calculator is asking in whatever terminology they use. If your still questioning the input value, put in an exaggerated value and watch what the calculator does with it l. You'll know which way to go from there.