Using the PCBWay 4 Layer custom PCB template, we can see in the stackup editor that a top and bottom copper thickness is specified as 0.035mm - akin to 35μm or 1Oz copper weight, which is the correct specification for PCBWay capabilities. Unfortunately, the gerber files are exporting that the outer layers are 0.5Oz thickness. I have attached the generated readme file from the gerber zip.