If you go back to that other thread, in the code, you'll notice a line that is in green font. That line will delete the "used" data from sheet 1 once the transfer of data is complete.
To activate that line, just remove the apostrophe at the begining of the line. I am assuming that you have copied it over to your code. If not, do so but make sure that it is in the same place in your code as the other.
If you prefer to keep the data in sheet 1, the other option is to refresh sheet 3 each time a transfer is done. So, in your code, just above this line:-
add this line:-
("UsedRange" is the data set. Offset(1) ensures that your headings are not deleted).
Either way, you should not end up with duplicates in sheet 3.
I hope that this helps.