The number following the size, in this case CXA, is the model number of the holder. As you can see in the catalog #1 is the turning and facing holder. Number 2 is the turning, facing and boring holder; it adds a vee groove to the bottom of the tool holding area to accommodate the round shank of a boring bar.
Yes, the numbers are just the style of holder. Turning; combo turning/boring with v-groove bottom; round boring bar holder; Morse Taper; Jacob's Chuck; multiple types of integral indexable insert; parting tool and plenty of others are options.