IBM 5251 Series Maintenance Information Manual page 194

Note: If the remainder in step 4 is 0, the self-check
digit is O. If the remainder is 1, the character
combination has no self-check digit. Ensure that this
character combination is not used in a self-check field.
Example:
Self-check field
Multiplier
Product
Sum of the products
Divide the sum by 11
Subtract the remainder
from 11
Self-check digit
Self-check field with
check digit
AF12765
2 7 6
543
2
2 42 6 10 28 18 10
2+42+6+10+28+18+10=116
116..;..11=10 plus a
remainder of 6
11-6=5
5
AF127655
8-2