What is the meaning of superstring

#1

CB number once detected should not be sub-string or super-string of any other CB number.
Ex- In 4991, both 499 and 991 are CB numbers but you can choose either 499 or 991, not both.
Can you elaborate on this?

#2

@prasadnitesh202 it means that u can not have a number of the string in two cb numbers like 4991 can either have 499 or 991 .similarly 1119 can have 11,19 as cb numbers