This is the property that should be databound to set the CurrentItem. By setting this property instead of SelectedItem, we can first filter the list that is the ItemsSource and then set the SelectedItem.
The amount of items to include above the selected item. If the selected item is at index 3, and this value was 2, the selected item and the 2 items above it would be displayed.
The amount of items to include below the selected item. If the selected item is at index 3, and this value was 2, the selected item and the 2 items below it would be displayed.