I have each of those resolutions listed twice. And each of those refresh rates. 60 75, and forget the third.
I have about 15 resolutions listed, just those three make up 6 of them.
And if I switch to one resolution that has a twin and Apply and accept that resolution, if I pick its duplicate the apply button doesn't light up. Much like it's just a duplicate text reference for the same 'object'.
As I said, it doesn't really cause any problems. Just an oddity I was wondering if anyone else had. (Figured since it was a Steam install, it should be the same.)