That is quite a while, but understandable especially if your computer is older. Try formatting on another computer to be sure.
Hard drive manufacturers typically define one gigabyte in powers of ten, that is 1 GB = 1,000,000,000 bytes. Computers recognize a gigabyte as 2^30, or 1,073,741,824 bytes. So 500,000,000,000 bytes divided by 2^30 equals about 465 gigabytes as seen by your computer.