It is a transparent rule of thumb: the score assumes roughly half an hour of real work per rating point, which lands most backlogs between 4 and 20 hours. Your actual pile may differ, but the estimate is enough to plan sessions, which is the point of the tool.

Because the pile returns when the system is a rare heroic event. Two focused sessions a week clear the backlog and build the tray-and-sort habit that keeps it clear, so the work you do stays done.

The overdue actions are the expensive part — late fees, expiry dates and missed renewals cost real money. Clear those in the first session, then the one-action papers, then filing. The tool lists that order in its checklist.