I want to sell my mom's iPhone 4S and need to know how many gb it has.

I want to sell my mom's iPhone 4S and need to know how many gb it has. It's an iphone model A1387 emc 2430 fcc id bcg-e2430a. On eBay people are also listing other model numbers that have no relevance to these numbers I pulled off the back of her phone. How do I accurately list it without those numbers?