Multiple DNS showing in ipconfig

Using windows 7 and pulling up the cmd prompt along with ipconfig/all the dns shows as

75.75.75.75

75.75.76.76

75.75.76.76

75.75.76.76

I'm trying to figure out the duplicate 75.75.76.76 showing. I've contacted comcast and they told me there is nothing to be concerned about. Any idea why this is going on? I'm using a XB3 modem/router. It also looks like a new update was also applied earlier last week.