The small hours are the stretch from roughly one until five in the morning, the part of the night where availability narrows even though nothing about the price or the arrival window changes.
The phrase is vague in ordinary use and precise here. The small hours are the stretch from about one in the morning until about five, the part of the night after the last of the evening bookings have started and before the first of the dawn ones. This site exists mostly for that stretch.
The fee, exactly. The arrival window of forty to sixty minutes, exactly. The deposit rule, exactly. Nothing in the house arrangement has a clause that activates at a particular hour, which is why nobody here talks about a night supplement: there is not one to talk about.
Choice. Forty-five therapists are on the roster and each of them keeps her own hours. Plenty keep late ones deliberately, which is what makes a booking at half past three ordinary rather than remarkable, but fewer keep half past three than keep half past ten. A request at that hour for any therapist who is working is straightforward. The same request for one particular woman may or may not be, and asking the two questions separately in the thread is the difference between a fast answer and a slow one.
Your own margin. Everything inside the small hours sits on top of a day that has already happened. A guest who books at half past two after a long evening should be honest about how much of the session they will actually be awake for, because a two hour booking slept through is still a two hour booking paid for. The note on the one o'clock second wind deals with the particular trap of feeling wide awake at exactly the wrong moment.
At the dawn window, which begins when the light does and behaves differently enough to have its own entry.
Two lines settle it: where the room is, and what time you want someone at the door. The answer comes back with a name, an arrival window and the whole figure, whatever the clock says.