Outside your hours, by default
Most offices are cleaned before the first person arrives or after the last one leaves. That is the arrangement unless you ask for something else: it is faster for us, less disruptive for your staff, and it removes the awkwardness of cleaning a room somebody is sitting in.
The surfaces that actually matter
A workplace is judged on the kitchen, the bathrooms and the meeting room, in that order, by everyone who walks through it. Those get the time. Desks are wiped where they are clear, floors are done every visit, and shared touch points are disinfected rather than dusted.
A scope you can hand to a facilities manager
You get a written list of what happens each visit and how often the less-frequent items come round: interior glass, vents, under-desk floors, appliance interiors. Nothing is left to be argued about after the fact.
