input: [0] Required 1st Step What happens if I mark the first step of the funnel as required in the settings? [Funnel Visualization] The required first step applies only to the Funnel Visualization report. When you mark a first step as required, the Funnel Visualization report only includes goal conversions that pass through that required step. Other sessions are just dropped from the report. If you see a conversion rate in other reports but a zero conversion rate in the Funnel Visualization report, this indicates that the required step wasn't viewed during sessions that converted. [Goal Flow] 
output: The required first step is not taken into consideration when viewing the Goal Flow report. For example, if a user skips the first step, then you will see a flow from the original dimension to the second step.