@31w You are a waged employee with a set schedule. If you were hired to complete tasks and leave at your discretion it would have been mentioned in your employment agreement, and you would have no issue with someone raising it to your manager. I have worked these positions before, it's totally fine. But that is not in your employment agreement. You are paid to work for eight hours, so you work eight hours. You can dance around that all you want, but you, me, and everyone else here knows you just left early because you didn't want to work. You use the excuse of being highly productive, but literally everyone that leaves early says that.
Now try again. We're anonymous here. Be honest.