Why is it possible to make 60 minute appointment 30 minutes before I go on break?

Today I set my break hours between 2 and 4pm. When I went to my site to check, I found that I was able to book a 60 minute appointment at 1:30pm which would mean that I worked 30 minutes into my break. What did I do wrong? I thought I had arranged it so that people need to allow 60 minutes before booking an appointment example they can't book an appointment at 2:45 for 3oçlock.
Thanks for any help.