How can I set times for appointments?

After clicking an available date, when the time slots appear, I just want a single time slot displayed (the one for 9.30am ideally), and I should like it to say 'book', rather than the time. Somehow whatever I do, the time slots begin at 8am, even if I put working hours to 9.30 to 10 for all providers.

The example I'm using can be found here: Is there a way to only have one available timeslot? Thanks.