There was a response to a question this afternoon which merited a downvote because the initial response was incorrect. However the author edited their solution to an acceptable answer, so I wanted to remove my downvote, by clicking the up arrow, thinking this would zero out the downvote. Instead it removed my downvote then added +1 for an upvote. How should I have zeroed out my downvote without casting an upvote? Just click on the number?
To zero out your downvote, you would merely click on the downvote button again, which would cancel your previous downvote.
If you had passed the time limit for undoing your votes, then you would have been unable to do so, unless the author edited their question as you had mentioned.