I have almost all the parts for the Zen ready, so I’m looking to dimension the table.

Just to double check before I cut pipe, the footprint in the calculator is the edge to edge space that the entire ZenXY will fit in. So in your sample table which is 36"x60", the no-kidding inner dimension of that cavity is 34.5"x58.5" which are the numbers to use in the calculator (minus perhaps some margin).