The # of Strings corresponds to the physical number of strings for that model. This should match the number of controller ports you plan to use.
The Nodes per String or Lights per String represents the physical number of light nodes, bulbs or pixels in each string. If the # of Strings is set to 2 and the Nodes per String is 100, the model will contain 200 total nodes.
The Center % is used to indicate how much area the empty area of the circle occupies. Decreasing it will drop the circles inwards and increasing it will push the circles outwards.
The Layers attribute value describe the concentric rings in the circle. This will create node count settings for each layer. The sum of the node counts must add up to the number of nodes in the model.
The default starting pixel is at the bottom of the circle, go clockwise on the outside ring and then the next inner ring wired and so on. The Starting Location can be changed to start at the top of circle, or start on the inter ring or run counterclockwise if needed.