The MonteCarlo_range_min and MonteCarlo_range_max are used to pick random starting initial parameters in Monte-Carlo runs. The parameter_limits_min and parameter_limits_max are absolute bounds the parameter cannot cross in fitting procedure. By definition max(range)<=max(limit) and min(range)>=min(limit). If you don't want to change some of these arrays: supply empty array [] in its place.
For details see source code in: Dataset.m