Buffer not working

Hi!

So I have set u the following

A service of 1 hour appointments with a 30 min after buffer.
Default time slot step: 30 mintues.
Use service duration for booking a time slot: checked.

Now I have set my employee availability for that service from 10:00 to 13:30.
In my calculation, the available time slots for the client would be:

10:00 – 11:00, (buffer 30 min) 11:30- 12:30, (buffer 30 min) 13:00 – 14:00.

But instead it shows: 10:00 – 11:00, not calculating the buffer, 11:00 – 12:00.

How do I fix this?
I have no company working hours (empty) and only employees working hours.

Pls help!