Confusion in question

#1

Here what it means by super-string, why 499 and 991 can not be CB number at the same timeā€¦
Please clear thisā€¦

#2

hello @ashishnnnnn
consider this number.
12345 (let say 23 and 34 are cb number just an example)

CB number once detected should not be sub-string or super-string of any other CB numbe

then by this statement they mean if u have considered 23 ( i,e 1 23 45) in ur answer then u can not consider 34 (i,e 12 34 5) (because 3 will overlap i,e 1 234 5)