You have 3 numbers related to armor that determine your armor points:
- Armor Rating - this is how much armor the physreps you are wearing are worth in armor points
- Maximum Armor Points - This is the maximum amount of armor you can wear. It is determined by your class and your ranks of Wear Extra Armor.
- Armor Tag - this tag will have a certain amount of armor rating that can be used as Armor Points
Your Armor Tag determines your Armor Points.
You can only use an Armor Tag that is equal or less than your Armor Rating and your Maximum Armor Points.