R6220 readyshare extremely slow

Recently tried using readyshare functionality. Setting it up was super easy, but write / read speeds are extremely slow. Between 4 - 7 mbps over wifi.

I don't know if it's a set-up issue or if that's the expected transfer rate. I've updated the firmware and Wi-Fi network is getting 250mbps over the internet. The drive I'm using gets 500mbps when connected to computer.

Router is : AC1200