hommealone on "IPN "Notification URL" to use in WP e-Commerce payment gateway (PayPal)?"

I'm setting up a WP e-Commerce shop in WP. (I'll be using the PayPal Standard payment gateway.)

At the (PayPal) payment gateway provider website, when enabling the IPN feature, they ask for the "Notification URL". What do I fill in there?

Should it be the root address of WordPress at our domain:
http://www.ourdomain.org/wordpressdirectory/

- or -

Should it be the address of our store's homepage:
http://www.ourdomain.org/wordpressdirectory/products-page/

- or -

Something else entirely?

Thanks!

https://wordpress.org/plugins/wp-e-commerce/