I'd be annoyed as well. It would just be shameful if it was only one product and an unfortunate spec error, but considering they have 2 larger sizes that are also quoted at 10.5 and 8.5 oz respectively...that seems like purposeful misinformation to garner sales.
If you want to give them the benefit of the doubt, you could contact the customer support and see if maybe you got a bad batch or something and see if they will somehow help you get down to the specified weight, but as a consumer that did your research, I tend to fall on the side of "don't cause me unnecessary hassle."
I would return them, if nothing else than for the seeming dishonesty. Put your money to a company that does a more careful job of monitoring the quality of their product (outsack has a quoted variance of +/- 0.1 oz from quoted weights and grubpack has an absolute max weight for their product).
DISCLAIMER: It pains me to advocate against a local AZ small business, so I'd probably temper my response more and contact Armored Outdoor Gear, but as a whole this shouldn't be necessary for such a simple product.