Commerce- How can I track order details (products, quantities) in PayPal?
Right now, Commerce PayPal does not itemize order information for PayPal WPS. We implemented itemized order details for Express Checkout in the 2.0 branch, but we currently just have a patch in a feature request to add this support to WPS. If you'd like to review it or follow along, the issue is here: https://drupal.org/node/1301570

In the meantime, your alternative could be to create a View inside your Drupal site that uses Views Bonus Pack to generate a CSV in the same format for your completed orders. That might even be a preferable long term solution, as it will work regardless of what payment method a customer uses to buy from you (in the event that you add additional methods).