Network Speed - 72mbps

Hi,

My network setup consists of a Unifi Edgerouter and 2 Unifi UAP wireless access points.

I have a Wireless N laptop on the network, and in the connection status it is 72mbps (not 300mbps as N should be).

All my wireless devices are Wireless N, none use G. There is no way with the AP's to set it to N only mode (its always mixed, ng).

Any ideas why this is happening?

Thanks.