After you place an order, the supplier will send you a proof. A proof is a document that shows a final version of your design with details about the dimensions, colors, materials, and print process.
The proof acts as an agreement between you and the supplier confirming the design and specifications of your item before it enters production. Manufacturing will not begin until you approve your proof.
The proof will look similar to the dieline you uploaded for your item, but it will be reformatted using the supplier's in-house software. The supplier may have made slight tweaks to the design to optimize it for manufacturing.