Double check with Everymac web site with Apple model listing - http://www.everymac.com/systems/apple/index-apple-specs-applespec.html
Sometimes when Apple specs. first come out they are listed for technology at the time. Somebody later brings out a RAM module that was bigger than Apple had available but people apparently got to work, so you'll see two listings of what was originally posted as maximum RAM (at the time) by Apple and what is now possible.
Note, if your computer is still under warranty and you upgrade it yourself you will likely void your warranty unless RAM is specifically mentioned as a user upgradeable component. Even then, if you installmore RAM than is specified things may get tricky. Vendors will use the least excuse to get out of warranty repair. On the other hand I know nobody at Apple will ever look at my computer again so I do all kinds of things to mine myself.