If you right click on your online orders value in the flow, and select create segment for this path; you will see the rules that are being used to generate it...
For a sample I threw together, I see a Hit Level segment, using:
"Page (non-repeating instance) Exists"
AND
(container: Visitor Level)
"Custom Metric Exists"
Which for me, yields me in between "all events" and "unique users triggering events" that I see in my Freeform Table (the segment doesn't seem to return matching values when used in my freeform)
To be honest, I'm not terribly fond of this visualization, because there is ambiguity in what is being represented; and when I can't create a segment that will match the values at each step, and have no way to explain to executives why... I just don't use it.