Custom designs are generated using a coordinate-exchange algorithm. The number of starts is the number of times that the coordinate-exchange algorithm initiates with a new design. See Coordinate-Exchange Algorithm. You can specify your own value using the Number of Starts option. Increasing the number of random starts tends to improve the optimality of the resulting design.
Unless you specify a value for Number of Starts and click OK, the number of starts is controlled by Design Search Time. To see how many starts were used to construct a design, click Make Design. Then select Number of Starts. The value in the text box is the number of starts used to construct the specific design.
In certain special cases, the globally optimal design is known from theory. If the coordinate-exchange algorithm detects that it has found an optimal design, it stops searching and returns that design.
Tip: To reproduce a specific design, you need to specify the Number of Starts and the Random Seed originally used to produce the design. Obtain these values from the red triangle options after you click Make Design.
In examples of custom designs in the documentation, the random seed and number of starts are often provided so that you can reconstruct the exact design being discussed.