Update coverage regex parsing details

doc/ci/pipelines/settings.md

@@ -118,7 +118,8 @@ job log using a regular expression. In the pipelines settings, search for the
 ![Pipelines settings test coverage](img/pipelines_settings_test_coverage.png)
 
 Leave blank if you want to disable it or enter a Ruby regular expression. You
-can use <https://rubular.com> to test your regex.
+can use <https://rubular.com> to test your regex. The regex returns the **last**
+match found in the output.
 
 If the pipeline succeeds, the coverage is shown in the merge request widget and
 in the jobs table.