Well, clearly the carbon has a higher atomic number, and that means this group attached this carbon has a higher priority than this group here. Likewise, let's examine the second carbon. The second carbon of the double bond is also attached to a carbon, and it's also attached to an H.
Which one of these two groups has a higher atomic number? Well, clearly, the carbon has a higher atomic number, and so the carbon wins. And let's label it with an asterisk. So notice that in this compound, our groups with the higher priorities are on the same side of the double bond.