Tethering data allowance from phone to laptop via usb
Let me see if I understand you:

[Router] &lt;--Wifi--&gt; [Phone] &lt;--USB tether --&gt; [PC]


If this is your setup, then what is happening is the Phone is acting like a router. It has multiple ways to connect to the internet (3G and Wifi) and it does not simply bridge the connection for the PC. Instead it does the same thing that your router does, which is NAT, or Network Address Translation. Basically, you have two networks: the network that's connected to the router, and the network that's connected to the phone's USB port (which has only one machine on it).  There is probably no easy way to port-forward from your router to your PC in this configuration.  The phone is its own computer; it is not a wifi-adapter, even though your PC sees it as just a network device.