Most POS systems do not support canceling online orders.
When an order is canceled on the Deliveroo side, it will be visible in your Deliverect account as 'canceled'. However, in some cases (e.g. when auto-accept is on), the order will immediately be processed in your POS as well.
In this case, you will need to manually void the receipt in your POS (e.g. Lightspeed) in order for your revenue to be correctly calculated and displayed.
A detailed description of how to do this can be found here.