Like Mako said, AAW stat is currently disabled.
AA gunners should be leveled with consideration for their reload stat primarly, and their accuracy to some degree. For MN, SN and RM it is simple to level AA gunners as they are just standard gunners, but for USN, RN, IJN and KM it can be more complex because classing to the AA classes which provide more AAW tend to slow the growth of the reload and accuracy stats. Most USN and RN players either just class their gunners as reload gunners and use D variants of the AA guns with AA shells loaded, or keep their AA gunners as armament sailors while their reload stat grows, until classing them as proper AA gunners to gain access to the AA specific guns. IJN and KM players rely more on competent AA and the specialised AA guns and dont have access to specialised Reload gunner classes, so they mostly tend to delay as armament sailors rather than class normal gunners. How soon you choose to class your delayed armament sailor as an AA gunner is based mostly on how soon you believe you can reach the reload cap, which can be done quickly if you invest in many experts and vets.
When it was working, the AAW stat of all sailors (all sailors in all slots) plus the ships natural AAW value would all contribute to a final AAW stat. AA sailors were the best at contributing, in a similar way to how all sailors contribute repair but repairers add the most, and again with restore. Due to the inability to properly balance the large range of AAW values that could result from this the sailor AAW stat was disabled, and now only the ships static AAW value is considered.