check source subnets , destination subnets ,ports , access details as per rules , if subnets are still valid definitely it is in use

if u changed subnets for site or access changed , you want to restrict some specific subnets then you can clean up unwanted the rules . mainly rules are already there for specific reason , unless you know the reason for rules don't modify

u can clean multiple entry .for example if u have supersubnet for specific smaller subnet than u can cleanup smaller subnets .only if rule are same