For the value column in Table 3.1, “Encoding Code Table”, the “value” is also called code, or character, or digit.
Start code = start character
Check character = check digit
Function code = function character
The variant is just the character set, so variant A/B/C is just the Character Set A/B/C
This item means the symboloy for UCC 128 or EAN 128, often can be write like this:
UCC-128 or EAN-128, UCC/EAN-128, UCC.EAN 128, ......
It is just a variant of Code 128.
More please refer to Section 2.8, “Other related info”