This is how security rules work:
Lets say you have following values in the value set attached to DIV segment:
500
501
502
503
504
You have following users in your organization:
USER1
USER2
USER3
USER4
Lets say you don't want USER2 to view or use the values 500 and 504 in any transactions.
You will create following security rule on the DIV value set:
SECURITY RULE1
INCLUDE: 000-999 (include all values)
EXCLUDE: 500-500
EXCLUDE: 504-504
You will assign this security rule to the responsibilities used by USER2. You will also enable security at the value set and also at the segment DIV.
Using this concept you can create security rules based on your requirements.
Keep in mind that security rules at implemented on a segment while cross validation rules are implemented on chart of account structure. If more than one segment are involved then you have to create security rules on multiple value sets.