It actually stands for DHL Ground Residential. When I first signed up for the devil site somehow I indicated my address was a commercial one and when the shipped me winnings via DHL it would say DGC (DHL Ground Commercial).I would guess DHL GROUND. But it could be something else entirely.
My last DHL shipment from c-bid arrived 3 business days after the estimated delivery date. I live in MA and c-bid is in PA. So, the whole shipping process should only take 2 business days. That shipment took 5.
I'm going to open a customer service inquiry and see if they'll ship my winnings UPS and USPS only.