The concept is you have 3, eight hour shifts per day, seven days a week. To achieve that you would have four (or more) work groups working 35 - 40 hours each, during that period. Line workers will be working 5 days a week but some of those 5 days might be Sat/Sun. I owned retail stores that were open 10 hours a day, 6 days a week, but my employees worked 40 hours, 5 days a week. There were overlapping shifts. However, I worked >72 hours per week sometimes.........even slept at the stores when called for!