what does "for five days each at scale" mean here

Question

In 2008, motion picture and television actors with speaking parts were guaranteed by SAG rules to earn at least $678 per day on  big-budget films and $504 per day on low budget (i.e. less than $2 million) films. Extras earned $110 per day. For instance, if an actor worked on two films in a year for five days each at “scale,” she would earn $6780 before deductions, per year. This is not enough to live on.