Hi Gonzalo,
Excellent question! In Doubleclick Studio, when you upload a file you can indicate an exit URL, however you may want to use the specific exit url you created when you made the ad in GWD. Choosing the "overrides URL" option overrides the exit URL in Studio and instead uses the one you set up in GWD.
Please let me know if you have any additional questions!
jaz
Program Manager, GWD