Only one property and one event per module can be selected User Interface Default.  'item' already has this attribute.  Selecting this attribute will void the previous setting.

You tried to set the procedure attribute of a property or event to User Interface Default but it was already set on another property or event. This can occur in the Procedure Attributes dialog box.

Only one property or event is allowed to have the User Interface Default attribute set at once. Click OK to make the current property or event the User Interface Default or click Cancel to void the change.