@4632215
If you have a /30 tunnel there can only be two IPs inside, one is the server, the other one is the client. So all is clear.
If the tunnel network is bigger, there can be one server and multiple clients inside. So you have to tell the server, behind which client IP he can find the desired network, you want to send packets to. This can be done by the iroute directive in OpenVPN.
In pfSense you have to create a client specific override to set this, where you have to state the client sides remote network.
But if you only have one client anyway, you can spare this and easily set the tunnel mask to /30.