These settings allow you to insert backups into the game once the outcome has been safely decided. There is a separate setting for when you're winning and when you're losing. The SimEngine will then give your 2nd string players more precedence to come into the game.
You may want to use this option if you want to help protect your starters from injury and/or to provide valuable playing time to your younger players. If your team is already young, you may not want to use this option so your players will get as much experience as possible regardless of the score.