I'm not big at Redhat but one is the old version and the other is the updated version. It does this in case the update doesn't work you can boot into the old version. The new appears to be 1) Red Hat Linux (188.8.131.52), and the old 2) Red Hat Linux (184.108.40.206-9). Those are Kernal version just look at the update and see which matches.
That's my opinion anyway. I would leave it for a while to make sure everything works then delete later. I'm not sure how in Redhat, sorry. At least you know what it is though.