Gary wants to connect to his home network over the internet so he can see his dog via his Samsung camera and talk to him. It requires uPNP to do this. Leo doesn't like uPNP because it has security issues with opening a port to the outside world. The problem is that it's automatic. If malware gets in, it'll open via uPNP and Gary will be vulnerable.
Leo says he can DMZ it or use as guest. Port forwarding is the manual way to do this, and is completely safe. So if he can find out the port that his Samsung camera uses, he could do it that way.