Different time intervals for booking in +appointment

I have two different kinds of services . The first reservation is at 1 hour and the second at two hours . The first works well. The other two hours shows two hour intervals , eg 6-8 and 8-10. This makes it impossible to select 5-7 or 7-9. I assume that the second calendar must be changed so that each hour is displayed ? But how do I do it?

Another problem with the current solution is that a reservation for an hour in one calendar means that two hours is recorded as busy in the second calendar