When a customer says that a sample is approved but they want the print location to go up 1/4 inch, just say no. In fact, say “hell no!”
There is a school of thought to say yes and they won’t notice, but I don’t agree. I tell customers that we load carefully and we load with lasers for correct placement. However, human beings put on shirts made by other human beings and shirts are not pieces of paper or metal but rather flexible stretchy irregular quickly sewn pieces of fabric.
One shirt can be printed to an exact tolerance, probably of less then a millimeter, but you need at least 1/4 inch tolerance to print lots of t-shirts. Get the placement lined up with a ruler, but then put away the ruler and don’t let the customer have you agree to a promise you cannot keep.