GL-AR300M Open VPN Speeds Low

Got the GL-AR300M running from a tplink w9980 router. Am using Digibit vpn in the open vpn setting. Now my download speeds are around the 10mbps. But if I use the digibit app on a phone or tablet am getting 25mbps. Now am wondering is there anything i can change in settings to achieve higher speeds from the GL-AR300M ? Am a complete novice at routers and some guidance would be very much appreciated.

Thanks in advance

10Mbps is not bad on the router. Your phone and tablet has a much faster CPU.