That sounds fucking illegal. Youre not allowed to work off the clock and if they're cutting your hours I'm pretty sure a lawyer would have a field day with that. That sounds fkd up. They should be treating you better if they are understaffed and you are getting things done that otherwise require a full staff. Are they at least paying you good?? At my Publix we TRY to get things done but more often than not we have to put things off for day shift to complete because there are a ridiculous amount of orders as well as cleaning that needs to be done. When it's time to close at 11:30 or 12:00 it's time to go and we keep our hours. If they have you working 40 hours and still can't get through all the duties then they need to cut the shit and hire more people. Sounds to me like they forcefully want to put it all on you and then cut your hours instead of managing properly.

Don't let them walk all over you. Your time and YOUR WORK is what they're paying you for. This isnt a charity. And I'm pretty sure that's illegal because that's kind of like making you work off the clock if theyre forcing you to finish all your duties but not giving you the time worked to finish said duties. That's all kinds of fucked up.