That looks more like a problem with a different part of your code. I think you should probably post some more code.
Notice that 70, 20, and 50 do appear in the output, and in that order. This tells me that they are inserting properly. But to me, their positions and all the extraneous output would indicate an issue either with the iterators that you're using or your output loop/statements themselves.
For Each ctrl As Control In Me.Controls("pnlMainPanel").Controls
If ctrl.GetType Is GetType(System.Windows.Forms.Panel) Then
For Each subCtrl As Control In ctrl.Controls
If subCtrl.GetType Is GetType(System.Windows.Forms.TextBox) Then
If subCtrl.GetType Is ...