This dialog box let you change some quantitative parameters in the model.
The demographic constant conditions the number of offspring produced by a pair of mate. This will directly affect he population growth rate.
The maximum number number of iterations for mating loop is used to prevent very long time for pairing calculation: you may change this value if you use very large population, or if individuals are very picky. But depending on numerical initial conditions, this value should prevent erratic behaviour, while impacting your reproductive output: not all individuals will reproduce if this threshold is reached.