property Items.DefaultItem as HITEM

Retrieves or sets the default item's handle.

TypeDescription
HITEM A long expression that indicates the handle of the item that's used by all properties of the Items object, that have a parameter Item.

The property is used in VFP implementation. The VFP fires "Invalid Subscript Range" error, while it tries to process a number grater than 65000. Since, the HITEM is a long value that most of the time exceeds 65000, the VFP users have to use this property, instead passing directly the handles to properties. 

The following sample shows to change the cell's image:

.Items.DefaultItem = .Items.AddItem("Item 1")
.Items.CellImage(0,1) = 2

In VFP the following sample fires: "Invalid Subscript Range":

i = .Items.AddItem("Item 1")
.Items.CellImage(i,1) = 2

because the i variable  is grater than 65000.

So, if you pass zero to a property that has a parameter titled Item, the group takes instead the DefaultItem value.