The phrase "full ounce" means to have the maximum amount or quantity of something, typically referring to a measurement unit called an ounce. Full definition
4 full ounces of shaving soap in 8 ounce container. (amazon.com)
Not sure what I did wrong, but the chocolate sauce, in spite of it being 6 full ounces of chocolate, only covered front and back of half of the cookies. (elanaspantry.com)
Premium quality 12 inch tall Warrior Knight figurine — Made from solid PVC weighing nearly 16 full ounces packed inside a custom printed display box with transparent window. (gamechup.com)