When working on a project, you will most likely have days off, such as weekends and holidays. These days should not be counted in the "Duration" column of the Project Chart.
You can adjust which days are off and which table columns are visible by clicking Properties in SmartPanel.

In the dialog box that appears, you can select the working days and a country whose holidays you observe.

You can also control which columns of the Project Chart’s table section are shown or hidden. You can change these settings at any time without losing any data; that is, hiding a column does not delete any data you enter into it. Click OK once you've selected the desired options in the dialog box.