Why do Feedback counts in Reports sometimes differ from those in the Flow dashboards?

Both figures are correct, they just reflect different time frame selection factors.

The Dashboard number reflects Feedback received for leads that were submitted in during the dashboard’s selected time frame. That’s because the dashboard is a primarily a display of lead submission activity.

The Feedback columns in Reports reflect Feedback that was received during the report’s selected time frame, no matter when the original lead was submitted. Feedback columns in Reports are based on the Feedback event’s timestamp.

To assure accurate accounting over time, you should always use one reference or the other. Don’t switch between the two.