The ETA on your order is the date the final milestone of the PO will be completed. The final milestone will vary based on the Incoterm you are transacting under. For example, if you are transacting FOB, then the ETA will be the date your order reaches your forwarder's container freight station.
The ETA will always include the time it takes to procure raw materials, produce the products, complete quality control, and package the order. The ETA will extend based on shipment time according to the final milestone of the PO.