AC.ID notation

I can't believe it took me ten years to think of this. 🤦🏼‍♂️
When I'm referring to Johnny.Decimal numbers in the abstract – that is, I'm just referring to any number, the system as a whole – I've been using xx.yy or 00.00 as a placeholder.

Area Category ID = AC.ID

The number is, of course, made up of your area/category combo before the decimal, then the ID after.
So now when I refer to AC.ID, I just mean any number in your system.