wx.Listbox and FlexGridSizer

The code below compiles and runs but i don't know where the docs are for FlexGridSizer so i can't find what the number "5" on the end of this line means:

flex.Add(New wxListBox.Create(panel, -1, strings,200,200,100,100,wxlb_single), 1, wxALL | wxALIGN_CENTRE, 5)

also why isn't the Listbox being positioned at 200.200 and 100*100 wide/deep?

SuperStrict

Framework wx.wxApp
Import wx.wxFrame
Import wx.wxAui
Import wx.wxListBox
Import wx.wxButton
Import wx.wxStaticText
Import wx.wxHtmlWindow			' this has the wxPanel in it...


New MyApp.run()

Type MyApp Extends wxApp

	Field frame:MyFrame

	Method OnInit:Int()

		frame = MyFrame(New MyFrame.Create(,,"wxAUI Sample Application", , , 800, 600,wxDEFAULT_FRAME_STYLE | wxSUNKEN_BORDER))

		SetTopWindow(frame)
		
		frame.show()
		
		Return True
	
	End Method

End Type

Type MyFrame Extends wxFrame

	Field manager:wxAuiManager
	Field notebookStyle:Int
	Field notebookTheme:Int
		
	Method OnInit()

		' tell wxAuiManager to manage this frame
		manager = New wxAuiManager.Create(Self)

		SetMinSize(400, 300)
		
		' add a bunch of panes
		manager.AddPaneInfo(CreateNotebook(), New wxAuiPaneInfo.Create().Name("notebook_content").CenterPane().PaneBorder(False))
		
	End Method

	Method CreateNotebook:wxAuiNotebook()
		' create the notebook off-window to avoid flicker
		Local width:Int, height:Int
		GetClientSize(width, height)

		Local ctrl:wxAuiNotebook = New wxAuiNotebook.Create(Self, wxID_ANY, width, height, 430, 200, notebookStyle)
		
		Local panel:wxPanel = New wxPanel.Create(ctrl, wxID_ANY)
		Local flex:wxFlexGridSizer = New wxFlexGridSizer.Create( 2 )

'		flex.Add(New wxStaticText.Create(panel, -1, "wxTextCtrl"), 0, wxALL | wxALIGN_CENTRE, 5)
		
'		DebugStop
		Local strings:String[] = ["1","2"]
		flex.Add(New wxListBox.Create(panel, -1, strings,200,200,100,100,wxlb_single), 1, wxALL | wxALIGN_CENTRE, 5)
		panel.SetSizer(flex)
		ctrl.AddPage(panel, "Glenns wxPanel", False, Null  )
	
		Return ctrl
	End Method
	
End Type

Cheers
Glenn