I don't know, I think "additional" is pretty clear.
From Dictionary definition:
"added, extra, or supplementary to what is already present or available"
in other words, if you understand English and trust the dictionary, it is unambiguously saying you need something THERE in the first place to add anything to it. Seems like plain English to me.
The game's definitions do not always, or often, strictly adhere to the dictionary definition. In fact they are defined within game context.
Besides, if you start with 0 and add 1 that is additional. It's added, extra, or supplementary.
Seems like plain English to me. (So maybe you should verify that your argument doesn't work as well against you as it does for you before being condescending.)