The Jira Data Center Performance Metrics article states:

The following tables show the relative performance of the various actions in the tests as the load increases for each JIRA instance configuration: JIRA Server (one node equivalent), two node Data Center, and four node Data Center. Each table shows the response time relative to the baseline response time which we determined to be JIRA Server with six browsers. 

However, there is no reference in the entire document to the baseline (one node equivalent) response times, the whole article operates with a percentile compared to that baseline. If I am not mistaken, the response times are specified in the Jira performance metrics article. If this is the case, please make sure to link it accordingly.