Appointment + / Setting fixed time values

Hello,

I need to set the timing of available appointments to fixed values, I'm uncertain about how to do this.

Right now it’s not in sync with the actual working hours.

http://anneliesdewispelaere.be/wordpress/make-an-appointment/

I have tried to play with the:
- Admin side time base: right now set to 15
- Time base: right now set to 45
- Added all the working hours, as described below.

But I can't get it to respond as I wish it would:

It's for a session time that is fixed: 45min

And working hours are:
Mon: 9:00-20:45 Break: 12:45 - 14:00 / 16:15 - 16:30 / 18:45 - 19:15
Tue: 8:30-20:45 Break: 13:00 - 14:00 / 16:15 - 16:30 / 18:45 - 19:15
Wed: 8:30-20:45 Break: 13:00 - 14:00 / 16:15 - 16:30 / 18:45 - 19:15
Fri: 9:00-18:45 Break: 12:45 - 14:00 / / 16:15 - 16:30

It is of importance that client can only get appointments at the following hours, for a period of 45min:

Monday:
9:00 - 9:45 - 10:30 - 11:15 - 12:00 - 14:00 - 14:45 - 15:30 - 16:30 - 17:15 - 18:00 - 19:15 - 20:00

Tuesday:
8:30 - 9:15 - 10:00 - 10:45 - 11:30 - 12:15 - 14:00 - 14:45 - 15:30 - 16:30 - 17:15 - 18:00 - 19:15 - 20:00

Wednesday:
8:30 - 9:15 - 10:00 - 10:45 - 11:30 - 12:15 - 14:00 - 14:45 - 15:30 - 16:30 - 17:15 - 18:00 - 19:15 - 20:00

Friday:
9:00 - 9:45 - 10:30 - 11:15 - 12:00 - 14:00 - 14:45 - 15:30 - 16:30 - 17:15 - 18:00

Thank you for investigating this issue.

Best regards,
David