For minimum wage jobs, when CAN and CAN'T you negotiate / be assertive?

Looking for a general consensus. From CA btw. My (18f) literal immature dumbass did training for 2 days, 12 hours in total, without pay, figuring it wouldn't matter seeing I'll get paid later. They said right off the bat they couldn't pay me for training and I went with it. The manager will be calling me later this week to discuss salary and other shifts. Should I inquire why the training was unpaid? Should I take this job if it's already obvious I look like an easy target?

Thanks in advance.

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