Appointments Time Base

Hi, my client need the following:
She have services of 7 hours long... so she can provide 2 per day. The problem in appointments is that if i choose 7 hours (420min) in base time... it doesnt let me choose an appropiate starting time in Working Hours. She starts at 1200pm and ends at 2,00 am. The plugin only let me choose 12am 7am 2pm & 9pm. I think it needs a parameter where you set your time base starting hour, in order to fix this behaviour