When you add a shift and do not manually enter the shift duration, it is "auto calculated" - meaning that the hours for that shift are set to be the exact time between the start and end time. For example, 8am to 5pm would be auto calculated to be 9 hours.
Sometimes if there is time between when helpers come in and leave (ex. a break or lunch) you will want to manually enter that shift's hours. The Auto Calculate check box is defaulted to On, but if you enter a number, it will not be automatically calculated.
You can manually add in the duration when you add a shift, or later you can do this quickly for a number of shifts or view how the shifts are all set using the Multi-Shift Edit schedule view. On that view, if you see "ac" next to the duration, this means that it was automatically calculated. You can quickly view this information and make changes to a number of shifts' durations on this view and then click the Save Changes button.
When you set your shifts' hours, and in future weeks you Import that schedule, all of the shifts will already be set to the correct hours helped. You only need do this once for your initial schedule week.
You can quickly add this information to multiple shifts using the Multi-Shift Edit schedule view.