This is an example of an family with an array that kinda mimics a curtain that opens and closes.
However – it is also a good example of what happens if you don’t create a fix for when an array drops to only one item. You need to formulaically stop this from happening, by doing something like this:
Applied Array=if(Calculated Array>1,Calculated Array,2)
(where Applied Array is the parameter applied to the physical array in the family, and Calculated Array is the number that is formulaically derived)