How to understand the netstat-n of Linux

The

netstat command is used to print the status information of the network system in Linux, which allows you to know the network situation of the entire Linux system
when you do not want the host, port and user name to be displayed, use netstat-n. Numbers will be used instead of those names

I tried the following:
first use the netstat-a command, and the result is as follows:

localhost:6379Redis

netstat -an:
![] [2]

does use numbers instead of names, but the port number of 6379 still exists, which contradicts his non-display port? How do you understand it?

Linux ubuntu
Jul.22,2021
The

n option displays the address and port number in numeric form, not by name.
goes further by using the IP address instead of the hostname (for the hosts recorded in hosts), and for some default ports, the port number is directly displayed instead of the service name, for example, the
ssh service is 22jue, the web service is 80th, Webrel SSL is 443, and so on.

-n means digital display

the following is quoted from man netstat

-- numeric,-n 

   Show numerical addresses instead of trying to determine symbolic host, port or user names. ,

similar to

-- numeric-hosts 

   shows numerical host addresses but does not affect the resolution of port or user names.

-- numeric-ports 

   shows numerical port numbers but does not affect the resolution of host or user names.

-- numeric-users 

   shows numerical user IDs but does not affect the resolution of host or port names.

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