Understanding Flow Chart Metrics and Event Calculations

Hiya, this might be a stupid question, but I'm confused as to how Flow charts are calculated. When I try to set a single step metric for a certain button press, I see 54 occurrences of it and all 54 have come from a Viewed event X before it. When I set the step metric to that Viewed event X, I see that it only leads to 44 occurrences of the same button press. How does that happen?