Router WAN speed limitation

I intend to buy a new router, this one in particular.

It says, it supports 802.11n protocol, so it could allow the transfer speed up to 300 Mbps between wireless devices.

Strangely, the WAN speed is limited to 10/100 Mbps.

Obviously, I intend to use the Inteet through Wifi, but if the device can support only 100Mpbs on wire and the Inteet is coming through a wire from the ISP (the ISP provides 500Mbps), I guess, the incoming Inteet speed will be limited to 100Mbps.

Am I correct?