To adjust the costs for vias in the autoroute algorithm. If you increase the value, the autorouter will try to insert less vias. If the value is to high, the autorouter may not be able to complete 100%.
To adjust the number of the first pass in the batch autorouter. The ripup-costs increase in passes with higher pass number.
To define the ripup costs in the pass with number 1. The ripup costs in the pass with the number N are (N * (Ripup start costs)).
To adjust for each signal layer the costs for traces in and against the preferred direction.