One of the critical steps when ordering a printed circuit board is specifying the copper weight.
The default, should you choose not to specify a weight, is 1.2 oz of copper. This is because customers routinely specify a minimum 1 oz copper thickness and 1 mil of copper in plated through holes. To achieve this, we routinely plate up .5 oz base material with .7 oz of additional copper which provides the requested thickness in the hole. Often our PCB board quotes will reflect this specifying .5 + .7 oz Cu/sq ft where the .5 is the base copper and the 0.7 is the plated copper.