The computer says that it is ATi Radeon HD 4600 series? If so, it's probably because either GPU-Z or Windows doesn't specifically recognise the GPU on the card, but recognises the GPU series - HD 4600.
It may be 4600 'Series'.
Where do you see it reading it as 4600?
Don't worry about that, inside "dxdiag' on windows and "gpuz", it is just says that my card is 4800 series instead of HD 4850... If your card is working well then don't mind it.