When shipping with DX Express you may want to use your Order ID as the shipment's consignment number instead of the Shipment ID. Shiptheory now has an option in DX Express' advanced settings section which will allow these to be swapped round.
In order to do this, go to your DX Express settings page. Navigate to the bottom, click advanced settings and scroll down until you see the Consignment Number option. Use the dropdown menu to select which ID you would like to use as the consignment number.