The Defense Screen contains a list of available Defense units with pictures and descriptions. It will say after the unit's name the number of units currently on the planet. The cost of the defensive unit, as well as the amount of time it will take to build are shown under the description. You can build additional units by entering the number of units you want to build of each type and the pressing send at the bottom of the page.
Unlike buildings, and technologies, defense units in production cannot be cancelled.
Defensive units and ships are both manufactured by the Shipyard and share the same production queue.
Commander Only Edit
It will show a resource in Red if you do not have enough of that particular resource. It will also tell you how long you will have to wait at current mine production before you can build that unit.