I don’t think this is correct. What you’re being asked to define here is ‘which external IP and ports should I be looking at, and when I recieve data from those, what should I do with it.
By specifying the external IP address of your PC, you’re in effect saying that only data that comes from that IP address should be forwarded. What you actually want to do is forward data from the IP address of your phone when it’s connected to your cellular network. Obviously you don’t know what that IP address will be, and it will change dynamically over time. So, what you probably need to define here is ‘Any IP address’. How you do this will depend on your make/model/firmware version of your router, but it may simply be a case of specifying ‘Any’ or using wildcards. The help guide for your router may help with acceptable options.
It may also be worth you reading this thread:
Whilst the whole thread will be of help to you, post number 30 onwards has some useful info about how some ISPs use a double NAT system which prevents you from achieving what you want to. The thread gets a bit messy, but it does explain how to find out if your ISP is using double NAT.
Pete.