I am trying to load items into two columns of a Combo Box but it does not work as I expect. All properties are their default values except ColumnCount = 2

FOR i = 1 to 10
this.Combo1.AddItem(STR(i),i,1)
this.Combo1.AddItem("Colm 2"+STR(i),i,2)
NEXT

The resulting columns are jumbled.