Everytime a new garment style is put in the production line, depending upon the complexity, there are some - make-ready-run setup time and cost. During this make-ready-run, there are some actual products that are not produced up to the mark.
These early products are taken out from the final production deliverables because they were being produced "during the set-up"
Think of a photographer who is setting up the camera. They take up few "trial shots" in the same setting - those shots are not their best work but those shots help them to refine their work flow and get ready for actual photoshoot - the make-ready-run losses are very similar.
This set-up / make-ready-run loss limits the production per SKU.
For a small factory, the SKU MOQs can be 50 to 100 pcs while for mid-size factories the SKU MOQ can be between 500 to 1000 pcs while the large ones can even have 5,000 pcs per SKU and above.