You did indeed get 500 GB. Just not the same format that computers use. When a retailer says "500 GB" they mean 500,000,000,000 bytes. Computers calculate storage differently.
8 bits = 1 byte
1024 bytes = 1 kilobyte (kB)
1024 kilobytes = 1 megabyte (MB)
1024 megabytes = 1 gigabyte (GB)
So if...