Working times are displayed incorrectly

Hello,
On the Website http://zinkundzauber.de/termine/?wcalendar=1491004800&app_service_id=1&app_provider_id=7#app_services_dropdown_title, the following possible times are displayed on April 4:
09:30 free, is correct
12:00 not possible, is correct
14:30 free, is correct
17:00 not possible, is correct
19:30 not possible, this is not right.

For the service "Workshop 2,5 Std. (mind. 8 / max. 16 Personen)" there is the service provider "Workshop 2 5 Std", the working hours "Workshop 2,5 Std" Has.

According to the working hours, a booking should be possible at 19:30.

Can someone please check this and check if there is an error in the settings or in the program.

many thanks for the support.

Best regards
Rainer
P.S.
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