Work time questuon

So when my boss made the newest schedule. She put my friday time as 2pm to 7pm.(i am 1 of 2 FT dishwashers at my place, and on friday and saturday . We have a 16yr old kid come in and act as our runner.) Now every other job I have ever had. That has a posted start and end time on the schedule. means just that End time rolls around, i punch out and leave. My boss tells me that she has to "Cut" me. at 7pm. What am I missing in this Equation?