Since you are required to label each box with a Deliverr box contents label, as a part of the receiving process, Deliverr will scan the unique identifier for that box. Once all your boxes are scanned, Deliverr will check that the expected number of boxes in your inbound exactly matches the received number of boxes.
If fewer boxes were received than expected, then Deliverr will email you a Short-Shipped Boxes notification. In addition, you will see a notification on the Completed Shipment page of the Deliverr Seller Portal.
You can then click on this notification and either confirm that boxes were short-shipped to Deliverr or request that Deliverr investigate.
Marking that boxes were intentionally short-shipped
Requesting Deliverr investigate