I suspect you made an error when you uploaded the model.
After the model has been uploaded, you need to select if the model is in inches or mm.
mm is the standard selection, so if you don't change it, shapeways will use mm.
The first image shows that the disc is indeed 0.66 mm where I would think your designer intended it to be 0.66inch.
The second image is a bit more complicated, because the shapeways person used inches in his model display.
it shows a thickness off 0.0258inch, which is the same as 0.66mm. Again, shapeways reads 0.66mm instead of 0.66 inch, and in their modeling software, it showed 0.66mm as 0.0258inch.
So it seems to me that the culprit is shapeways reading your model as modeled in mm instead of inches.
So I'd suggest to try reuploading the model, then make sure you select inches as the model unit, and try printing it again.