Our HDD Docking Station support offline clone. Clone means the target drive will totally be same with the source drive. So you find 80G from your 500G drive. Because this 80G space has been partitioned and renamed, and the 80G space shows on you computer. However, the rest of 420G space is concealed. If want to find the concealed space, you should partition and rename them.
Go to the storage- disk management-- find the rest of 420 G -- right click on it --change drive letter and paths -- add drive letter or path -- assign the following drive letter.