Question about new router

I just bought and setup my new router today.
I got it from Walmart today for $125.
We were told it's a pretty decent router, especially since it's a trade up from Comcast's default/basic modem/router.
For some reason though, the speeds are slower now. Dropped from 20 mbps to about 8 mbps.

This new router is called, I think, ARRIS: Surfboard SBG6580 (Lost the box)

I placed router in a good place, no extra shit running, etc. I took all precautions.
Can anyone tell me why this would happen? Can it be that it's just updating still since it's new?
Here's a picture.

http://postimg.org/image/evny0lji1/