reading SCAR 17S user manual. says critical i know what barrel i have. how do i know?

http://imgur.com/9wZ2dvB

there is a link to a screen shot of the digital user manual. how do i know if I have S, CQC, or LB? i try not to make assumptions but I would guess "S" stands for "short" CQC stands for "close quarters combat" and LB stands for "long barrel". however since i have a SCAR 17 S maybe that S stands for something related to this "s" barrel i may or may not have" then again my barrel is 16.5 inches and so would that be a "long barrel" is that even what that stands for? lol. sorry i am a noob. how do i know what barrel i have? out of S, CQC, LB? I am just a civilian, i do not have a Class III license, this is a semi automatic SCAR 17S.