Rule number in wlan mac filter

When we create a rule in mac addres filter enable, we create a rule using add object instance but when we delete that object instance, by default the rule number increments automatically. For Example we created two rules in WLAN MAC filter, and we delete the second rule so by default the new created should have the number 2 but when we create this rule the rule number comes out to be 3, it gets incremented automatically even though second number rule has been deleted. So is it a bug in genieacs or what?

The CPE is responsible for device instance ids, not the ACS.