For what purpose MerchantPreferences has setNotifyUrl
I noticed that when creating billing plan you can set NotifyUrl for MerchantPreferences. I have already enabled IPN listener for some url (URL_1). If I set NotifyUrl with another url (URL_2) for MerchantPreferences I expected that messages will receive to that url - URL_2, not URL_1. But it's not, I still receive messages to URL_1.
So, for what purpose MerchantPreferences has setNotifyUrl and how use it?