ORO.OPS.FTL.105 Definitions:
‘Duty’ means any task that a crew member is required to perform by the operator, including flight duty, administrative work, training, positioning, and standby.
‘Duty period’ means a period which starts when a crew member is required by an operator to report for or to commence a duty and ends when that person is free from all duties.
These are the new regs, but all the old ones said the same somewhere. No idea why anyone would think that office time counted as any more or less than 1 to 1. Time on duty is time.