This page has a few notes on Fuego's charting features, for users.
Charts are produced during the "processing" phase of test execution. This is done after the test results have been parsed from the test log and the results placed in the unified output format (run.json) file.
See Jenkins Visualization for information about charts that are produced for the Jenkins interface. See process and chart_config.json for information about the variables and files used for chart creation, and how they can be customized.