Port forwarding is such a mess. Every router seems difference and some vendors it is not even consistent between their routers.
This is one of those go read the online manuals or try to find one of the simulators for that router. It is more which do you like the best. Some are actually too complex in some ways, it makes it hard when you just want to forward a simple port. Some allow you do fancy things like have multiple servers in your house and use different external ports but each use the same internal ports.
Both tplink and asus have fairly advanced stuff but again they can be confusing.