qos-contraints

Good Day, does anybody have an example of how the qos-contraints configuration works, please? Not from a MOS/r-factor perspective but actually how and when the realm will start applying constraints based on percentages set and what the values in major and critical factors play and to be honest what the range means? I can't find an example how the defined values would have on media flowing through the realm and at what instance it would start taking affect. Hopefully this makes some sense. Thanks, Mark