If you wanted someone to gather your sheep together you could write the instruction in set notation this way. Denotes is an element of or is a member of or belongs to. A is a subset of B.
The colon means such that.
A collection of elements. A 37914 B 91428 such that. At the left end of each interval use with each end value to be included in the set solid dot or for each excluded end value open dot. You can pick one just according to the requirement.