First, hit me up with any questions. I'll give you no-bullshit answers. I can answer 99% of them and the other 1% I'll find you the answer within 24 hours.

You're getting fucked over.
Your manager doesn't know how to make a schedule. Your manager has screwed up in training and execution because you should be leaving at 10:15. Additionally, if you're routinely late closing they should use half of their brain and leave 1-5 slush hours in their payroll budget. But they clearly don't care and your DM isn't checking his EBRs for payroll because they're pretending it's fine.

You're in a tricky situation. Your SM is clearly violating policy. Your DM clearly doesn't give a fuck. My recommendation: Notify your District Manager. Notify your Area Manager. Notify your Regional Loss Prevention Manager (Violating policy regarding Wage and Hours is an indication of in-store theft and other integrity violations.) Call your HR rep, notify them of the status. Record the call. Request an investigation. Request additional training to prevent the issue in the future. DOCUMENT EVERYTHING.

ATLAS documents your punches at the terminal. ATLAS documents their edits in the computer. CCTV logs offsite. There is proof of all of this.

If you fight for back pay you will magically lose your job. You have two choices in reality: Do what I've said to fight for fair treatment, or find another job. I know of one person who this has happened with, she followed my advice, her SM was asked to resign, and she is now the ASM in that store. Your SM is supposed to make up failures to maintain the schedule or store out of their own time, because they are salary. YOUR SM CAN AND WILL GET INTO TROUBLE FOR BEING LATE IF YOU REPORT IT.

It's disjointed, but theres my advice.

Fuck ERC, they're useless.

PM me your area/region. I know you don't have my DM because he'd have fired your SM already. If we have the same Area manager I can advocate for you.

Oh yeah, notify everyone at once. Make sure you're on time. CYA.

Count your drawer when you start. Insist that it go in the safe or office where it is monitored. If they're lacking in integrity they'll probably try to can you by screwing with your drawer.

Top comments regard the legality of the situation. That's all true, but it's likely nobody cares and if you don't do as I've instructed regarding your two options you will regret it.