ANSWERS BELOW

Are the 23 digits of useless information always in the same position in the
field? Like always at the end or beginning or is it random?

AT THE END OF THE FIELD, BUT EACH ROW OF THAT COLUMN DOES NOT ALWAYS HAVE
THE 23-D

Also, what is in the field? Is it exclusively the 15+23 digits? or is there
other information?

THERE IS OTHER INFORMATION + THE 23-D (the 15-d was just for illustrative
purposes)

Thanks!