The router default the max transmit WiFi power is 30dBm, but the different countries, the wifi power limited is different; you can refer to the below steps to change the wifi country code to get the max WiFi power if you need.
The European countries have limited the WiFi power to a lower level.
Please log in to the router admin.
Go to Network > Wireless.
Click the “Edit” button on the 2nd row of the master SSID.
Click the tab of “Advanced Settings”, choose US or AU on the “Country Code”.
Then you can set the WiFi output power to maxed level 30dBm on the General Setup tab.