TAP-Windows Adapter V9

I have 300Mb internet speed I am running an OpenVPN when I connect to vpn I get 90Mb speed I did go to (TAP-Windows Adapter V9) is running on 100Mb I did check another vpn (Astrill VPN) their adapter (Astrill SSL VPN Adapter) running on Gigabit speed is 100Mb the max speed for TAP-Windows Adapter V9 if not how to increase the speed on TAP-Windows Adapter V9.