appointments+ hours not working correctly

Hi,

I have the plugin configured with a simple working hours of
mon-thu 8:00 AM to 11:00 PM
Fri-Sat 8:00 AM to 12:00 AM

Base time of 30 minutes set

and a service set up of 120 minutes.

As you will see at:
http://landmark.randompixelmedia.com/make-an-appointment/

on Friday and Saturday, the last appointment available blocks out 120 minutes or 4 slots, which is how it should be, but on Sun-Thu it blocks out an extra hour for a total of 6 slots.

Can you help me understand why this is happening and how to fix it?

Thanks,
Chris