Yep. The concentric boxes are all centered on the Avr (Average) point of the 3D grid. Its X, Y and Z coordinates are half the X, Y and Z dimensions of the 3D grid and used as the ‘S’ (Start) input to Series, which counts down in increments of ‘Xcell’, ‘Ycell’ and ‘Zcell’, respectively.
The number of concentric boxes is determined in the cyan group (below, not grouped in the code I posted), which sorts the ‘X Count’, ‘Y Count’ and ‘Z Count’ values to find the smallest one, then takes half of it.
It turns out that you don’t need to use ‘Odd numbers’ for ‘X Count’, ‘Y Count’ and ‘Z Count’. Those sliders can have ‘Slider type’ set to ‘Integers’. Even numbers may result in the smallest box encompassing a 3D grid of points instead of a plane (2D grid) or line.