Unassigned charges in report "Timekeeper Contribution and Collections"

When I run the report "Timekeeper Contribution and Collections", a column of "unassigned charges" appears. It is my understanding these amounts appear because of flat fee arrangements. However, why are they appearing under a specific timekeeper, if they cannot be applied to slips (because of a flat fee arrangement) ? How can I locate these unassigned charges? 

Also, there were some clients under the "client breakdown" that appeared under this specific timekeeper, when the timekeeper didn't actually have any time billed under the client at all. Why is this happening?