@YPL 

The advertized speed is a maximum potential combined link rate.  It is not the internet speed you will see.  For 5GHz specifically the maximum possible Linkrate is 1300 Mbps.   Internet speed has several factors you have to consider.  Number one is the internet speed package you pay for.  The maximum internet speeds will usually never exceed this.   Next you have to consider the band you are on, the capabliites of the client device's network adapter, the distance from the router and the network enviroment and any interference or congestion you are expericancing.  If you can provide more details we would be happy to help look into your concern?