OK. I see how you're getting there.
Shouldn't the second calculation be [Quantity>2] instead of [Quantity>0]? If you have only one participant, 1>0 and will trigger the third part. In your sample, 2 is greater than zero and succeeds in that 2-2 = 0 nullifying that part but only works of quantity = 2.
There is also an add-to-cart element that does not use this calculation. Is best practice to add the two columns and add a separate calculation just for this part? (the separate part is that participants can make a deposit of $500 per person to hold space -- the rest is payable later). I can show you the sample page.
Thanks for your help again.