Hello thank you for reporting this bug.
After some investigation, it is indeed throwing out an error massage,
looks like this is the bug that someone else was mentioning but in another way, he was saying that the CPS stop working after a while from every refresh of the game,
and i couldn't find why, so thank you for providing this error massage, looks like you do know how to code :D ?
anyway, this bug will be fixed today as a hotfix if possible.
Answering your question: The Adder will produce a % of what you currently gain from the Addition Task, meaning leveling up Addition Tasks will increase what the bot produce