The client is able to reject your checkout proposal and submit a new one (with the corrected times), after which you can accept them and resolve the situation. The best way to fix this is to immediately contact the client as soon as you’ve realised that you’ve made a mistake. The invoices will only be produced and paid for after the checkout has been completed.
What if my checkout has already been completed?
Unfortunately, it’s no longer possible to adjust the times for you. The best way to solve this is to compensate for the missing hours with a future shift at the same client. Talk to them about what they think is the best option for both of you.