First, is this a 4 speed 01M or a 5 speed 09A transmission?
There is a special method with a special filler container (VW tool # 1924) and OE diagnostic tool to fill the transmission and set the correct level, otherwise you can ruin the transmission.
If you tell us which transmission you got I can send you the instructions, but without the factory tools and diag. computer you can't really set the correct fluid level.
If there is no leak at all from the transmission and you still have the drained ATF, I'd suggest to measure the volume exactly and put the same amount back. You have to use the OE VW fluid. When you go to the VW dealer to buy the ATF you also have to ask for the ATF filler plug securing cap, it's only few bucks, but you can't reuse the old one.