On the daily-break-down graph of your test, you can view the base line performance of the test (in addition to the performance for each variation).
The baseline data can be seen for each metric (CTR, ranking, impressions and clicks). It is represented on the graph by dashed lines.
The baseline is the performance of the metadata previously set in your Wordpress. The date for it is pulled from Google Search Console and it represents the combined average of the last 30 day’s performance.