Ascii doc syntaxes not provide consistent output & not working as expected

Question

I have a .adoc file and it has a table with 3 columns. The table simply represents some HTTP codes with their status code, meanings, and methods.

This is the code I used to generate the above table.

[cols="10%,70%,20%",options="header",]
|=======================================================================
|Code |Meaning |Methods
|[[status-code-502]]{502}|
Gateway error response code indicates that the server, while acting as a gateway or proxy, received an invalid response from the upstream server.
|{ALL}

|[[status-code-503]]{503}|
Service Unavailable - service is (temporarily) not available (e.g. if a
required component or downstream service is not available) -- client retry may
be sensible. If possible, the service should indicate how long the client
should wait by setting the {Retry-After} header.
|{ALL}

|[[status-code-54]]{504}|
Gateway error response code indicates that the server, while acting as a gateway or proxy, did not get a response in time from the upstream server that it needed in order to complete the request.
|{ALL}
|=======================================================================

My question is when I'm using the same structure of code, why do the codes 502 and 504 show like "{502}" & "{504}", and without anchor tag and bold text? Appreciate it if someone could explain this and give a solution.