I'd like to see your source where "increased by" strictly means "to add" because if you say something has "increased by three times" does that mean you're adding three times to it? no, it means you multiply it by three. By the same token "increased by 300%" is quite ambiguous.
The math was never the issue here; the only thing in question is how the English translated into Math, thus a language barrier. (the true meaning of "increased by")
Perhaps you are the one who was truly confused all along?
completely unnecessary.
