Open Bookings, then Opening hours and services. Set each day’s opening and closing time, and press Save opening hours. It will tell you how many new slots it created.
Closed days
Leave a day blank and the assistant treats you as closed. It will not offer slots and it will say when you next open, rather than taking a booking you cannot keep.
Holidays
Block the dates before they arrive. A festival, a long weekend, the week the machine is being serviced. The assistant keeps booking into them otherwise, and the first you will know is a customer at a locked door.
Outside hours, the assistant still answers
This is the point of it. At eleven at night it still replies, still answers questions, and still takes a booking for tomorrow. What it will not do is promise someone now.
The time is your time
Times are in your own timezone, set once for the business. A customer messaging from elsewhere gets your hours, which is what they are asking about.
Change them when they change
Hours drift — a new late evening, a Sunday you stopped opening. The assistant will keep offering the old ones until you update them here, politely and wrongly.