How do 'time changes' for employees work at magic kingdom?

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For example, if my out time is 12:15 (I am able to leave early sometimes) and the coordinator changes my time so I can leave earlier, when can I clock out? I'll login to CDS, and it says I've been bumped out, but there is no option to click the clock out button. Nor does it tell me when I can clock out. Can someone explain to me in detail how the whole process for time changes works? I asked, but they only told me that Magic Kingdom has a 12-minute paid walk time, and it didn't make sense to me.