In the core RM rules, that table represents the specific armors and types of armor that are available.
In the core rules, one AT == one specific suit of armor.
Now, having said that, Armor Types 7 and 8 are Reinforced Leather Armor, and Studded Leather armor COULD be considered to be part of those two (these two ATs are pretty much the most versatile because they are more vague in their descriptions, allowing for variations).