Range behavior tells the software what to do if it finds a range specification for levels for an attribute for a product specification. Most of the time, people using the simulator just specify specific attribute levels that describe the product to be simulated.
But, there is a more advanced way to use the simulator, if you want. For example, let's say for a single product in your market scenario, for the attribute "Price," that you specify a range of 100-150. That is a range of price to examine over multiple simulations. In that case, the software needs to know what "Range Behavior" to apply when it finds a range of levels rather than a discrete level definition. Those simulations can be done just by trying each price between 100 and 150 and reporting the results (sensitivity analysis) or by conducting a search across prices 100 to 150 to maximize some goal you have specified (optimization search).
My guess is you have not specified a range for any of your product specifications (for example, the attribute price has a specific level to use rather than a range) and in that case, it is irrelevant what you set the range behavior to be.