Barcode problem

I would like to know how Corel Draw identifies if a bar code is Code 128 A, Code 128 B or Code 128 C, since there is no option of choice for the user.
I need to generate a barcode sequence from 118584645, it's 7 characters, Code 128 always works in pairs, in other programs a zero is added at the beginning of the sequence identified by the scanner, 0118584645, so that characters are in pairs, but in Corel Draw this does not occur.
Would anyone know how to explain it to me?

How does the Corel Draw barcode verification tool work? How to use it correctly?

Thanks.