Mhz Number Reading confusion

Just bought this Gigabyte Radeon 9600XT 128MB and looking at some of its comparison with its 256MB twin brings up these Memory and Core clock readings like:

Core Clock: 250MHz/500Mhz

Memory Clock: 300Mhz/600Mhz

what does the slash say? or how come there's two indicated number readings?

thanks

I think it just seperates the card info. The 250 and 300 are for the 128mb card and the 500 and 600 are for the 256mb board.

Not positive but almost positive that's the way it works.