Dexterity Modifier Cap (Dex Cap)
Source Player Core pg. 245
This number is the maximum amount of your Dexterity modifier that can apply to your AC while you are wearing a given suit of armor. For example, if you have a Dexterity modifier of +4 and you are wearing commercial defrex hide, you apply only a +2 bonus from your Dexterity modifier to your AC while wearing that armor.