What is Additional?

Legal Definition
This term embraces the idea of joining or uniting one thing to another, so as thereby to form one aggregate. Thus, "additional security" imports a security, which, united with or joined to the former one, is deemed to make it, as an aggregate, sufficient as a security from the beginning. State v. Hull, 53 Miss. 626.
-- Black's Law Dictionary
Legal Definition
Added, supplemental, coming by way of addition. See Ann. Cas. 1912C, 1007.
-- Ballentine's Law Dictionary