Thank you for posting your query in the Community. By default, UPnP is enabled on the modem which facilitates an application to automatically forward a port. There is no harm in deleting those entries.
If you don't use applications that need port forwarding you can certainly disable it. The UPnP can be disabled by navigating to Basic/Gateway Function menu.
You can manually do the port forwarding for applications that require access to specific ports for proper functioning.