You are correct Murphy. File/Option/Settings is to set the conversion rules for days to hour, weeks to days, months to days. When the duration and work values of tasks, resources and assignment is other than hours, Project converts that the values to hours using these conversion rules. These converted hours of duration are spread across days by using Project calendar. In your example, File/Option/Settings you have set the conversion rule for 1 day to 7 hours and Base calendar (set as Project calendar) is Mon-Friday, 9 am – 1 pm, 2 pm – 5 pm (7 hours). So, when you enter the duration is 2 days, the duration set internally is 2 x 7 hours = 14 hours. Then 14 hours is spread across two days using the Project Calendar. Hope this helps.