By Slack-TimeSlack time is defined

By Slack-Time
Slack time is defined as the time difference between a job's date-required and its current completion date on the
scheduling board. If a job is running late it is said to have negative slack time. When you re-prioritize using this
method, jobs are first sorted using its slack time value. Jobs with the same slack time are sub-sorted by their
current priority. Priorities are then reassigned based on the sort-order, and the board recalculated.
You can perform this command several times to really average out degrees of lateness. Once again groups are
preserved but may occupy different positions on their rows afterwards.