I know this has been asked but i still don’t understand meal breaks on 30hr new contracts

So I have to work the 6 hours i’m contracted and a 30 minute break unpaid. If i clock in at say 8am and work up until 2pm with no break then i have worked my 6 hours and i still have my unpaid meal break left of the day. Can I or can’t I go home 20 minutes early? Do i have to sit in the DO for 20 minutes and then clock out? Thanks in advance for any help 🙏🏼