Scheduled Overtime is an overtime which is preplanned by management for the next working week (so employees can anticipate their overtime involvement). In other words it is overtime that is scheduled in advance: this includes any hours worked over 40 within a specified workweek (40 hours is a commonly accepted standard on workweek duration).
Extra hours are usually compensated at a rate which is equal to one and a half time of the regular hourly rate of the employee. There are different attitudes to scheduled overtime, including laws that regulate it (overtime limits per day, constraints on number of days which can be worked with overtime in row, compensation rates, etc). By scheduling overtime, employers can get prepared to intensification of workloads due to certain reasons, for example an anticipated peak of customer activities.
Organizations which value proper level of quality and take care about welfare of their employees aspire to minimize possibility of scheduling overtime hours, or try to balance them in a maximally wise manner, not only because they are compensated at a higher rate, but also because prolonged overtime periods may exacerbate employee problems such as absenteeism, accidents, and fatigue, hence a quality of workmanship can decrease.