They simply didn't word that listing very well. 12/C means any chamber shorter than a 12/LC. There has for a long time been controversy over which mark a 3" chamber would have, but not a 2" one. A 2" chambered gun would bear the 12/C mark as would a 2 3/4" one. A 3" chamber would for sure carry the 12/LC mark leaving the 3" the only one really in question.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra