It's the Paper, Stupid --Dickeson

Want the granular detail for the WIP? Then track the time of make-readies, stops, delays, production and queue-time between production stages. Is it important to know this detail? Depends on your desire for continuing process improvement and how much profit you want to make.

Forget all notions of holidays or weekends, or chargeable or non-chargeable time. Time is time, an hour is an hour, regardless of what you call it.