Odd Internet speed problem

So this is a good one.

I have a user that has a 60mb down/5mb up connection that they are paying for in their home. They are hooked up to a Asus RT-N13U router. They have a laptop hooked up by ethernet and when I performed tests on several different speed tests, I did not get past 21mb down/1mb up.

When I checked the users providers speed test(Charter Communications) the test came back almost perfect matching the speed they are paying for with them.

So then I went ahead and bypassed the router and did a direct connection and all of the sites reflected the correct speed.

I'm thinking the router is probably the problem but before I recommend that, I can't help but wonder why the customers ISP shows the speed as right behind the router while the others do not. I checked the routers settings and I did not see anything that would bottleneck the speed.

Any ideas, opinions, or suggestions?