Kibana visualization how to customize the mapping?

like this. the legend display 5000 or 1, but I want to display "success number or failed number"?

You may need to create a scripted field that returns "success" for the value 5000 and "failed" for the value 1.

Actually, once is merged, you will be able to go into index patterns, edit the field, and apply the "static lookup" field formatter to display the 5000 as "success" and the 1 as "failed".