It looks like your order started processing for shipping on the 17th, which is when the PDF was triggered. However, during the subscription run each month, the warehouse is processing lots and lots of packages. They process things in waves and it is hard to pinpoint where in given package is. This is why this shipping confirmation email says that it should leave the warehouse by the 26th.
Additionally, the tracking information can sometime takes a bit to update after it ships out. You should see tracking information soon, if you haven't already.